Television shows are smarter than they've ever been before. The Sopranos, The Wire, Enlightened, Girls, Justified, The Shield etc. These shows couldn't have existed in the 70s or the 80s because networks needed to cater to such large audiences. Now that we have more options we can have smarter shows.
Amen. You don't even have to go for the prestige stuff. Nostalgia aside, does anybody really
think that "Adam-12" or "Dragnet" was smarter than "CSI" or "Castle"? That "Medical Center" and "Marcus Welby" were better than "Grey's Anatomy"? That "Petticoat Junction" and "Gomer Pyle" were smarter than "The Big Bang Theory"? That "Charlie's Angels" and "The Love Boat" and "Three's Company" were smarter than the average episode of "The Americans" or "Lost Girl" or "Warehouse 13"?
Bottom line: there's more dumb stuff out there, but a lot more quality stuff as well.