In general? Yes, I think TV has gotten dumber. People watch a whole lot of “reality” TV, and that’s where a lot of money is made. That’s a whole lot of dumb we’re talking.
When it comes to the very best shows? Maybe not so much. There have been trade-offs, for sure—try making a show have a real statement, and even assuming you get away with it, you’ll be covering very little ground that hasn’t already been trod and done better.
But savvy audiences today pick up on cues much faster than savvy audiences of the past; the language of film that’s been wired into us since we were kids is faster than the language of film that was wired into our parents if they had TV when they were a kid. Ever seen a decent 50s TV show? There may have been some smart people behind some of those things, and I don’t doubt many of them were smarter than people behind today’s shows, but the shows themselves are paced for people to keep up with, and that pace was slower. Not to mention that what people typically watched was most certainly a “vast wasteland” then, too, so don’t feel like you’re missing much there.
Much more now than 20 years ago, continuity between episodes matters. The audience is expected to remember things now more than they were then, and it drags you in deeper. Myth arcs are now a common feature of American dramas, but in the late 80s and early 90s only a handful of American shows pioneered that—and a lot of suits (and writers!) really did think it couldn’t be done in America unless you were writing a soap (completely ignoring that British and Japanese audiences had been doing it
just fine all along).
In recent memory, TV news is longer than 15 minutes, C-SPAN is a thing,
Lost experimented with being so crazily interwoven even the writers had to resort to looking things up on wikis,
Futurama cooked up some genuine math,
House was pretty good for a few seasons (except when it goes strictly formula or turns into a freaking soap opera), I’ve been hearing a bit about
Mad Men as a postmodern epic,
and I don’t even watch very much TV at all. (Oh, and fairly consistent quality producers like the BBC and HBO are still kicking ass and taking names; that never stopped being a thing.) Good TV is still around if you’re into that sort of thing; you just have to look pretty hard is the problem.