As people have said in the last few posts, generally speaking all the characters that were in the first series, have simply become the generally worst character trait over time and nothing else.
Jeff isn't ever really a nice guy who will do something mean now and then, he's just mean. Britta isn't a nice friendly quirky person who is sometimes stupid and sometimes a bit OTT about some cause, she is now only stupid or into a cause. Troy isn't cool at all anymore, he hasn't really been into chicks lately(though that is partially explained), and as said acts like a 5yr old when he used to be 10. Same goes for all the characters, they used to be characters with funny/quirky traits, now they are just caracitures of their old characters.
The multiple time line ep was mostly great, and the Troy gets the pizza timeline was nothing short of god damned amazing. But in the first series there were 10 episodes that good, in series 2 it was maybe, at a stretch 5, in series 3 its basically that single one so far.
I hope it gets a 4th, even as "bad" as it is compared to series one its still miles better than most comedies on tv. I'd freaking love it to get back to its best, get back into the more college/campus/community feel rather than just those 6 and stop focusing on all their negative character traits as its way to limiting, and honestly, kill off Shirley, far prefer to see her go than Pierce.