Unfortunately the writing seems to be getting worse and worse over the years. There were lots of nerdy jokes in the early seasons, but at that time they were done in a celebratory way. In many of the newer episodes it feels like mocking. See "Vault of Bones" for example. Not to mention all the "preetreen drama" introduced.
I agree that it dipped briefly after the first season, but lately the show has had amazing maturity and depth. as well as being hilarious in a slightly less zany way.
