Star Trek has certainly been a roller-coaster of ups and downs over the years. I have mixed opinions on some things but I'm a big fan overall, especially trek from the TNG-DS9-VOY era. I'll give some of my opinions on each series, in case anyone cares.
Enterprise (since it's the topic of this thread) - I hated the concept from the very beginning, because it largely represented the end of the unbroken, forward progressing line of continuity that had existed from TOS, through the TOS movies, and TNG (and TNG movies), DS9, and Voyager. The only exception being Nemesis, a TNG movie that came out while Enterprise was on the air. With that much existing continuity (everything from TOS, TNG, DS9, Voyager, and related movies), the idea of doing a prequel was insane. They boxed themselves into a corner because if anything truly exciting happened, it would immediately raise the question of why no one ever talked about these events in the future... At first they mostly tried to stay within the bounds of existing continuity (what had already been established in other series and movies) but the series was pretty boring. Later they brought in the Xindi and the Temporal Cold War, etc which was definitely treading on "how come none of this was mentioned in the future?" territory.
I didn't have any issue with Scott Bakula. Actually, I thought he was possibly the best cast person on the entire show and I thought he made a great captain - to the extent that he wasn't handicapped by bad writing. On the other hand the rest of the cast was pretty bad. You had Jolene Blalock who was just the token babe with zero acting ability playing a character that had zero depth or intrigue. The obviousness of the one and only reason why her character was on the show was cringe-worthy. Every other character was mostly boring and/or stereotypical. The fake and forced friendship between the helm and operations officers. The over-acting doctor. Everyone else, mostly forgettable.
The last episode of Enterprise was REALLY dumb. The idea of doing some kind of TNG holodeck flashback wasn't what bothered me as much as it was the fact that they tried to pretend that this occurred during the TNG series, on the Enterprise-D, wearing those era uniforms, despite the fact that the cast members had clearly aged beyond that. It was pretty cringe-worthy, and you can tell that even the actors themselves thought that it was stupid. They could have simply used the newer grey uniforms and had it take place on the Enterprise-E instead of trying to pretend that it was ~1994 again.
TOS (The original series) - I thought it was okay. I can see how it was groundbreaking for it's time. I grew up watching TNG/DS9/Voyager though, as well as the TOS movies, but I didn't actually watch the three seasons of TOS until later. I think this show is probably better if you watched it during it's prime and you have some built-up nostalgia. Watching it for the first time in the 21st century though, I thought that there were many parts where it had not aged very well, and were almost painful to watch. Still, I have a deep appreciation for the example that it set, and the fact that it's continuity was continued unbroken into the TNG/DS9/VOY era.
TNG - Probably my favorite Star Trek series. Season 1 was a little rough. Great cast, great charisma between cast members, and good writing overall. Also, I love all the fantastic guest stars they had over the years, with many people including Bob Gunton, Ronny Cox, and even Kelsey Grammer having the chance to play captains at certain points. Biggest downside of TNG, IMO, is that it is the series that created the "mirror universe". I simply hate the entire "mirror universe" concept and pretty much every single "mirror universe" episode is absolutely terrible. Also, while I liked the character of Data a lot, I think there was a bit too much focus on that character, at the expense of others.
DS9 - I liked this a lot also. More edgy than TNG, that's for sure. For me the show hits it's stride in Seasons 4-6. Then all of a sudden toward the very end of season 6 and much of Season 7 things just go downhill. There is still a lot of good in Season 7, but it feels almost like driving down a road with huge pot-holes in it after you just got off the freeway...
Ezri Dax- I did not like Jadzia being killed off, but introducing this new character for season 7 was just terrible. Here we are, the last season of the show, in the middle of the dominion war, where we still have tons of unfinished arcs from the first 6 seasons of DS9, and in some cases even arcs from TNG (Gowron, Worf, O'Brien, etc) that need to be wrapped up. Instead, part of every episode (Ezri was in EVERY season 7 episode) and in several cases entire episodes were wasted introducing this useless, obnoxious, annoying new character. I would have loved to have simply given other cast members like Martok, Garak, Nog, Rom or others more screen time instead. I get that they needed a certain minimum of female cast members though - only legit reason I've ever heard. Maybe they should have simply made Leeta a main cast member somehow? Could not have been any worse than Ezri.
Vic Fontaine- WTF? I don't know about you, but it's pretty lame to watch Sci-Fi about a 24th century space-station in the middle of an intergalactic war only to be forced to constantly indulge what was obviously one of the writers obsessions with early-mid 20th century Jazz music. Every time he is on screen we have to sit through what seems like an entire 5 minute song, I guess because he is just so amazing
Kira and Odo- This just never came off as natural for me, and in most cases sort of made me cringe. I think part of it is because Odo always gave me that humble grandpa-style vibe, and that isn't the sort of character that works well for making-out on-screen all the time. Maybe it's also because the actors never really thought it was a good idea either and you could always sort of tell via their acting.
Dukat religion- I liked Dukat a lot more earlier in the series when he was a more complex character that even had a bit of good in him. When he devolved into a much more simplistic, almost stereotypical, evil religious bad guy, the character just wasn't as interesting anymore IMO.
Klingons- I was a bit annoyed that they took a year-long break from the Dominion War story to focus on Klingons instead - to tie in when they brought Worf onto the show. Although they did eventually wrap the Klingon arc into the overall Dominion War Arc, it just seemed like an unnecessary season-long detour.
Mirror universe- This was only one episode thankfully, but one too many. I hate the entire mirror universe concept, particularly the way they shoe-horn in "mirror-universe" things from the regular universe regardless of any logic. The mirror-universe certainly is not unique to season 7, but it is another wasted episode that should have been used to help wrap up the series.
Voyager - I liked this show a lot overall. I thought it was slightly annoying when they introduced 7 of 9 as the token "borg babe", but they actually did a good job writing for her character and she did a good job acting (unlike Jolene "botox-lips" Blalock). I thought Janeway was a good captain, and Kate Mulgrew did a good job acting. Chakotay's character was a bit shallow. Kes was annoying and I was glad when she was gone.
My biggest gripe with Voyager was how it ended. The show spent 7 years setting the stage for what would happen when they get home. Yet instead of getting any resolution whatsoever to any of those questions, the show literally ends instantly once they get home.
Would the EMH remain as a respected crew member and friend or would he simply be deactivated/replaced? We even had a Star Trek episode where they tried to introduce some sort of "all of the old EMH programs have become slaves" narrative, yet we never get to see what happens to the Voyager EMH. This lack of resolution becomes an even bigger deal once you see the direction they went in "Picard" where artificial life forms were banned. Does that mean the doctor was deactivated / banned?
A bunch of the crew are former members of the Maquis. Would they be able to retain the same ranks they were given on Voyager? Would they face any prosecution due to their former roles in the Maquis? This isn't just some side plot, it was one of the main plots on the show and we did not get any resolution whatsoever.
There are countless more examples.
I would have liked to see Voyager get home maybe 1-3 episodes before the series ended. Have the last few episodes take place in the Alpha quadrant. Maybe the Borg followed them home and then they have to work with Starfleet to stop them. Or maybe an episode like "Family" which came right after "Best of Both Worlds" on TNG. Really any ending would be better than what we got. The show was about the crew, not the Delta quadrant. In it's current incarnation it feels like reading a book with the last few pages torn out.
Discovery - I have not watched any of this yet. Frankly, the entire concept of an animated Star Trek series seems extremely dumb and so far I have not been able to get over that hump. Maybe some day I will force myself to watch it.
Picard - I have very mixed feelings about this, but more negative than positive. First and foremost, it just really does not have the "feel" of a star-trek series.
-The show is way too serialized, to the point where it feels more like one long movie that was simply chopped into hour-long segments. I'm glad that I binge-watched the entire first season at once, because I don't think I could have handled waiting a week between episodes with that level of obnoxious serialization. I remember people criticizing DS9 for becoming semi-serialized during the Dominion-war arc, but they at least still made an effort to give each individual episode it's own little sub-plot. "Picard" doesn't even try.
-What Genre is this supposed to even be? "Picard" felt like it was trying to be some kind of weird action/horror/thriller instead of a Sci-Fi show. They repeatedly brought back old characters simply to turn around and kill them off. They seriously brought back the character of Icheb (one of the borg kids from Voyager) JUST so that we could watch a 5-second video of him getting his eyeball graphically ripped out of his skull?!? VERY lame. The character of Hugh was probably the best part of the entire first season. The actor did a fantasic job of portraying hugh and I think even portrayed it better than he did in TNG. But then, of course, they kill Hugh off...

. And then we get the mandatory ninja-fighting scenes, characters cussing and doing drugs, etc, as opposed to actual compelling story.
Roddenberry-era Star Trek was about showing what humanity could achieve, and maintained a largely optimistic and positive view of the future. "Picard" on the other hand goes out of it's way to depict a very dark and dystopian future where the flaws of society and the flaws of every individual character take front stage. Even when they brought back Riker and Troi, they couldn't allow that happy nostalgic moment to exist without shoe-horning in some depressing back-story about them having had a kid that died
What happened to Dr. Crusher? By the end of TNG they had practically set Picard and Crusher up to eventually become a couple, and in the last episode, "All Good Things", when they depicted the future, they were actually married. Then in "Picard", we get no mention of her whatsoever.... umm ok.
-Why did they obsessively need to re-design everything? Every computer interface apparently has to be some cheesy holographic interface now. Aside from the 1701-D flashbacks, we don't see a single "old" federation starship in the entire series. Are we to believe that every ship that existing during the TNG/DS9/Voyager time has now been retired? In the scene near the end where Riker and the fleet show up, every ship in the fleet was exactly the same, some boring new ship design.
The whole premise of a "rag-tag" bunch of losers on some small crusty little ship just makes the show feel like it's trying to be some kind of firefly knock-off.
Hopefully the new seasons take a different direction that is more like what you would expect from Star Trek and less like a bad Robocop sequel.