Perhaps it's not so much there isn't as much quality TV on these days, but that there is just more reality/makeover etc.. shows. Which gives the perception that there is less quality.
That is only on the Networks, on the cable channels we have had some of the best TV shows ever:
The Wire, Game of Thrones, Breaking Bad, Boardwalk Empire, Homeland, Justified, etc.
We even have online series that have great TV shows, like Netflix with House of Cards.
Anyone who says TV is worse now then it has been the past, is clearly not looking in the right places. If anything we in are in a golden age of television.