Gee, I never thought about that. You're right! Just goes to show that sometimes they would throw logic overboard if it helped to construct a crisis for the crew to face. Generations did the same (Picard going back to five minutes before doom on Veridian III instead of, you know, any earlier date) and Nemesis, too, of course.
Aside from that, all my theories for the failure of the TNG franchise have already been eloquently covered here. I'd like to add that the idea seemed to be, starting with First Contact, to not make these TNG films, but what Rick Berman thought of as Star Trek films. They sacrificed the ensemble they had in favor of a TOS-like setup which didn't work for TNG: Picard and Data never had the rapport that Kirk and Spock had.
But scope is also important. The TNG films felt small. Especially the one whose story was the biggest (FC with its apocalyptic alien invasions and the time travel to save the birth of Star Trek itself) felt like a bottle show. Few locations, and unimpressive location shoots, and of course a script that missed out on an adequate introduction to this supposedly massive threat. We get a Captain's log telling us the Borg are dangerous, but we aren't shown. You don't do it like that in the movies. That was a general problem for many of these films.
