First Contact had the Borg, that's probably Trek's biggest seller in terms of storyline. Insurrection's fountain of youth idea was a slight step down from that.
The problem is that they couldn't come up with any interesting TNG film scripts outside the Borg. They did the movies just because they thought Trek fans would watch anything. If they don't care, why should we?
TNG was far better as a show than movies. I'd rather watch any of the countless great episodes from the show over any of TNG movies.