I think the OP was referring more to educational material on channels like Discovery and History giving way to fiction based shows. Not that fiction based shows are "getting dumber". That's a different topic.
Yep. I remember when A&E and History Channel had a lot great stuff that actually had history documentaries. No offense to anyone that likes Pawn Stars, Auction shows and Pickers et al..
But wasn't the History Channel, for a time, the Hitler Channel? WWII, JFK, Lincoln, The Civil War and the War for Independence made up the bulk of their broadcasting.
And all these channels started losing viewers, TLC, HC, AP and other were losing viewers (Except during Shark Week). Along came a programming executive who started changing the programming, Hitler was regulated to around the time of VE Day, The Pacific Front to the week with December 7th, the Civil War to Lincolns birthday or his assassination, JFK to what ever week had November 23rd in it. This programming executive then started shows that appealed to larger audiences. Pawn Stars (which at least has a tiny bit of history in it) and others. The executive then moved from network to network making similar changes. Everywhere she went, ratings rose.
TV has gotten both smarter and dumber, History Channel has been able to come up with good miniseries on history using the revenue raised from Pawn Stars and others like it.
Using the History Channel as a example, who thinks it would have continued to survive had it stuck to its old format? I don't. Let those less interested in History subsidize the better history programs we have today.