I frankly blame the writing staffs
for the lack of quality more than Berman. Because even with him in charge they still managed to come up with some fantastic stories now and then (even on VOY and ENT)-- so clearly it WAS possible to do. They were just horribly inconsistent at it, and had probably been writing for Trek waaay too long.
And yeah, it was a mistake switching from Ron Jones to the wallpaper sound on TNG, but I can understand Berman's reasoning there. Jones' big, swashbuckling scores were great, but seemed suited more for TOS or the TOS movies, and Berman probably felt TNG needed to sound a bit richer and more sophisticated-- which I think those later seasons definitely do, thanks to the more atmospheric scores.
And I have to say, I've been rewatching DS9 lately, and I think they made that style of music work really WELL for them. I can't imagine Jones' style of music working nearly as well on that show.