It wasn't so much Insurrection
as it was that TNG really couldn't hold its own as a movie franchise. Both Generations
and First Contact
had major draws--Kirk meeting Picard and the Borg on the big screen, respectively--but the subsequent films didn't and had only the TNG cast themselves as the big draw, and it wasn't enough.
to that a growing disinterest in Trek by mainstream audiences and too many cooks stirring the pot behind the scenes, a downward turn for TNG movies was probably unavoidable, IMO.