I do wonder if 'mass market appeal' is
a large part of it. FC clearly tapped into something that the other three TNG movies quite frankly didn't (GENS had the benefit of coming off the back of TNG ending and the crossover with Kirk, but internally
it was arguably far too inwards looking to have true mass market appeal). NEM screwed itself over by advertising "A Generation's Final Journey...", subconsciously planting the seed into the minds of casual movie-goers that it was another naval-gazing exercise for the fans rather than a good movie in its own right. I'd actually say NEM had the potential
to tap into the same broad appeal as FC, but as I say they fumbled the ball.