It's that stupid environmental message and that REALLY poorly thought out conflict. The Ba'ku really should have been the more antagonistic, and the story should've been Picard attempting to relocate them. Like that one TNG episode.
Come to think of it, this movie has no reason to exist. They already did it in a much superior TNG episode!
Twice: Homeward Bound, Journey's End, (DS9) Progress. Even (DS9) Children of Time is a riff on a similar theme.
I like Insurrection, it's a TNG movie--as in a TNG episode on the big screen. But, yeah it does fall apart if you start analyzing things in it.