TNG's ratings were good enough to let the show go on for a few more seasons. But they were making less money on the show the longer it went on with syndication paying less and all the actor salaries were going up.
Doing those mediocre TNG movies seemed like a bright idea at the time. But in hindsight TNG probably could have gone on a little longer, the later spinoffs never reach those kind of high ratings ever again. Paramount probably were scratching their heads at why the later shows didn't catch on as much.
The writers really streched themselves too thin with TNG S7, DS9 S2, VOY preproduction, and Generations. All those things suffered for it during that era.