TNG was getting tired. The "same old thing"... zipping about your known quadrants and dealing with ever more "desperate to be creative" alien encounters. The cast was also getting tired. You could tell this in their performances, for the most part. Also, the episodic nature was getting tired too. DS9 introduced a more serialized approach and VOY picked up on it to some degree.
VOY started out well, but stumbled in the early seasons. Once the Kazon and Seska were out of the way, it began to "get going". Sure, it wasn't perfect and there were some characters easily disliked (like Neelix, although I think it took many seasons of character building to begin appreciating him more), but I thought this was a good series in many respects.
TNG ended when it should have. It was time.