Apparently free TV has indeed lost quite a bit of "intelligence" but why? It's the age old question of the chicken and the egg meaning did the TV networks start with dumb shows and people liked them or were people always this dumb and TV only found out in the last years?
Fact is good shows usually cost much money.. good actors, good writers, sets etc and it's not guaranteed to be successful (my best example is Firefly). TV networks are are a business and like all businesses they don't like risks and this industry is far more risky than a food or clothing industries so they turn to safe products which are cheaper and that's reality TV.
If you want challenging shows that need your undivided attention and a little bit of effort to follow them then you need to turn to pay TV, i.e. HBO and all the others where you can still get quality TV.
With the whole media landscape in flux due to internet technologies and changed viewer habits you may need to look a bit harder to find some intelligent programming but it'll always be available.