I think the ball was dropped with GEN. That was one awkward, strange film that just doesn't sit right no matter how you slice it. And this is from someone who sees a lot of good in GEN. So, you had millions of people watching TNG, which was a character driven sci-fi drama thingy, and the first feature film is half about Kirk, who has nothing to do with TNG, Data plays with his emotion chip, and the ship you've identified the show with for 7 years is sacked.
They didn't do anything with the characters, and de-branded TNG somewhat by crashing the ship. Really, nothing significant happens with the characters until NEM, by which point those millions of people had long since stopped caring. They stopped telling their stories. Should have had the wedding and Data's death in the first film. And just kept giving reasons to care or be interested in these characters while the crazy sci fi thing is happening.
I agree that neither INS or NEM are to blame, but TNG had lots of places to go.
This is kind of what I mean. You raise a good point about the most significant parts of star trek happening with Nemesis.. But when you think about it, just changing the dynamic isnt really enough to say you're going into new territory.
-First Contact was great but would have been better if they used the Borg Storyline from Star Trek Destiny. Here would be significant "new territory" since it closes out the borg arc
-Doing something significant with the Q continuum (like they lose their omnipotence and simply become immortals stranded on the planet in innsurrection. Closure to the Q and plenty of material for the extended universe to play with.
-William Shatner wrote a book called "The Return" which was centered directly after Star Trek Generations. If you subtract the ridiculous borg origin story, the general premise of the romulans resurrecting him would have been a better centerpiece to Star Trek Nemesis..
My point is even ideas like those wouldnt come from the TNG writing team. Id wager they were just burnt out.. and when that happens to any show, sharks start to jump and pigs start to fly..
I also agree that by the time insurrection and nemesis rolled around, the general audience had lost interest in star trek. First Contact while the best of the new films, really did lose steam. Plus there was interest in other franchises to consider (star wars was hot and heavy, firefly was popular.. I think battle star galactica had spun up again)
Whats also sad about the newtrek movies is there werent really any memorable lines like in legacy trek ("KHAAAANNN!", "You klingon bastards! you killed my son", "You will, and always have been.. my friend")
Have high hopes for JJ Abrahms though.. Star Trek 2009 is in my 10 ten.. I cant wait for this summers sequel