I have a really difficult time justifying these kinds of ideas, that society or some aspect of it is being dumbed down, when so much GREAT stuff is out there as well. Hard to find, granted, but great nonetheless.
No, I think what's popular in entertainment nowadays has no bearing on the intelligence of society, just different things amuse certain people, and now is the time of simple jokes. I, for one, enjoy bad puns, because something about how bad they are is indescribably hilarious. Call it, maybe, humor nostalgia. A lot of these things would have been genuinely comedic in a simpler time, maybe subconsciously, I'd like to be entertained so easily. Or maybe it's just a response to how tough things can be, that some people need to find humor in the smallest thing?
Regardless, I wouldn't call it stupid. Simple is a better term.