Absolutely agree, and upon reflection that kind of makes sense as Ron Moore and Braga were ascending in the last two seasons of TNG and then in power for the movies. Their lack of experience and youth led them to be lighter in both style and substance.
Don't want to sound curmudgeonly, however, in television during the TOS era you had writers who had life experience that, in many cases, had included military service (and possibly war) then a career path that had them doing stagecraft and radio and short stories. By the time they got to TV they had a lot of life under their belt, a sense of classic drama and practical wisdom in storytelling. The rise of folks like Ron Moore and Braga signaled the era of college only knowledge and then largely just perpetuating what TV was doing.
The design of TOS and TNG was such that, unlike any other television series going, they could truly tell any type of story … if they chose. They could do L.A. Law one week, E.R. the next, Indian Jones the next, a fusion of genres the next week etc. and it would have been true to the premise of the show, but towards the end of the TNG you had writers who didn't yet have the chops or ambition to fully explore the gift their job presented. Basically, I don't think they had anything they felt they needed to say so they didn't. Unfortunately, Star Trek is at its best when it IS saying something.
Sorry for the ramble.