Originally when TNG ended and Generations was being produced, I (and pretty much everyone else) thought that was a great idea. The TNG cast, like the TOS cast, were logically making the transition to films, and DS9 would be able to pick up the slack for the small screen.
The reality of course was very different. DS9 and every other Trek series that came after it just got lower and lower ratings, while the films were anywhere from moderately successful to complete bombs.
So I changed my tune. I felt that instead of making the films, they should have continued TNG, but with a new cast. But since most TV shows that have a cast change after so many seasons inevitably get cancelled anyway not long after (and the fact that Voyager was basically the same as TNG anyway but for a different cast and ship, and that show was no ratings bonanza), that wasn't really the answer.
So basically I'm left with, "The transition to films was the right thing to do at the time...they should have just made better films." And, "They should have stopped producing TV Trek series while the films were being produced, and produce one show only after the movies had run their course, thereby putting all the money and focus on that one show, theoretically making it a better show."
Which, unsurprisingly, seems to be what is happening now.