Well Star Trek V, like Star Trek: Picard is a good example of why you shouldn't let actors into the writer's room. It's a different skill set. I suspect the actors' agents had a hand in all the TNG movies and thus why Picard and Data got more to do than everyone else. By the time we got to Nemesis we had two Picards and two Datas eating up the screen time.
With the TOS movies, we should remember that The Motion Picture was really just a reunion show for the old TV show. All the characters were retired and moved off (well, not all, but the trio) and you had to come up with a compelling reason for them to reunite. They had to do it again in II and it was stretching credibility but at least in III and IV they were continuations which felt fairly natural. And at the end of IV we had a nice conclusion but I'm not sure it really seemed realistic at any rate to put a crew full of our core characters back into active duty for regular missions. Forget that Kirk was demoted to Captain, but Spock was also a Captain who should have his own ship and McCoy was still retired, wasn't he?
It's kind of like when they did that new batch of X-Files a year or two ago. They had to go dig Mulder and Scully up out of retirement just to consult on one special case going back to their time at the FBI. And then the next week they were both active field agents again, for some reason.
So to go to V as just another mission as usual felt wrong in the first place. Again in VI they had Spock as special liaison ambassador request his old crew so there was a reason. And sure the special effects in V weren't up to the usual we'd seen in II-IV at least. But the story was, as they said, a rehash of a story we'd seen many times. The humor and all the character bits seemed out of place, like Scotty not being able to find anything on his own ship. Sure, it's a new ship, but he'd be the quickest guy to adjust, not the slowest. It's just dumb comedy.
But it's just the Shatner/Kirk ego thing with the plot being that he's the only one who can withstand Sybok's brainwashing, because he's Kirk. That's a pretty lousy showing for everyone else, and why Nimoy and Kelley forced it to be changed to all three. Especially after the opening scene sets them up as a trio that can't function without all three. Kirk's not complete without them.
Ironically the scene where Sybok revisits Spock's and McCoy's inner pain was probably the best scene in the movie. Too bad they didn't get to peek at Kirk's, it might have been revealing.
The article touches on Shatner and Nimoy's contracts stating they had to get equal treatment so that's why they had to let Shatner direct after Nimoy did. Another footnote that Harve Bennett mentioned on one of the DVDs is that they also had approval over anyone else playing Kirk and Spock. The original idea for VI was a Starfleet Academy story with young Kirk and Spock but I think they couldn't get Shatner and Nimoy to agree on anyone so they couldn't do it and had to hire them back for another round. I think they were still consulted on JJ Abrams' reboot years later.
So the problem with V is that it's just an episode and not a very good one. From the script, the direction, down to the special effects and even the acting.
Now Nemesis to me failed on a lot of other levels. I think the early promise was that after lots of Klingons in the movies we were finally getting to see the Romulans, which to me was interesting. They had been set up fairly well on TNG but not overused. But when we finally get the movie, the Romulans are pretty much all killed off in the first 5 minutes to make way for a new big bad of some current writer's creation, the Remans, whom we have no connection to. And worse, they are being led by a human. And it's a clone of Picard. It's weirdly trying to introduce a foe with some personal connection and history with the main character, Picard, although there is no history or connection since it's a brand new character. And they got a young man so it didn't even do Patrick Stewart any favors by letting him play a dual role. With both Shinzon and the Remans it's a clear example of trying to wrap your new character in some veneer of something that fans care about while you, as a writer, don't care about any of that, and just want to create something new for yourself.
Spiner gets the actor's dream of playing dual roles. Weird that they have all the crew say "oh my gosh, it's another android like Data" like they've never seen that before even though they've met Lore like 4 times and Data's mother. I think the best scene in the movie is the one where B4 is stumbling around Shinzon's ship and then you realize it's actually Data when he raises his eyebrows. But for the rest of the movie, B4 is only there to give Data a "remember" type get-out-of-jail-free-card for his death.
On a technical level of special effects and maybe even dialogue and pacing, it's probably better movie than V. But there are so many scenes where you suspect the writers either don't know much about Star Trek or they just don't like Star Trek. Like have Picard tearing around on a pre-warp planet in a dune buggy drawing attention, because they thought Trek needed a dune buggy. Like asking Troi to allow herself to be mind-raped so they could find the location of the enemy vessel. Why not just track its plasma exhaust or something?
So I find them bad for different reasons. V was executed worse, in a way, but Nemesis maybe had more potential that was wasted. I don't know.