I think one of the big flaws of the TNG movie run was that we were never given the chance to "miss them" the way we were with TOS.
Also, coming immediately off the back of an almost universally acclaimed Series Finale, where TOS was cancelled with little fanfare and ended without resolution so we were interested to see where the characters go next. As open ended as "All Good Things..." tried to be, it tied up the characters well, and the glimpses of the future within it were also well received. Almost anything following that would struggle, but maybe moreso when the goodwill of "All Good Things..." was still fresh in movie-goers minds. I don't know how long a gap they should have taken, but a gap was needed, to give audiences a chance to enjoy "All Good Things..." and build anticipation for the crew's jump to the big screen. Generations ends up feeling underbaked and anti-climactic as a result of the rush to get it out before the end of the same year the show went off the air, and a certain amount of that fatigue plagued the following movies too.