I'm just over it.
It's not just that the writing isn't as good. Though I think that is partially what it is, but even when it's up to Season 2 or Season 3 level greatness at times, I still don't laugh the way I did back then because the shtick has gotten old. "That's what she said" isn't funny anymore. Neither are the pranks. Neither is Dwight's whole nature man commando thing. Even Michael's social retardation doesn't make me laugh like it used to. It's a combination of my fickle and disloyal nature and the fact that after five seasons, those jokes just really do not hold up anymore, and I think that's the real core of the recent Office backlash. I have a few additional problems with the show too, though.

I miss Jan.
I just do, that's all. She's always kind of been my favorite supporting character, and I like how she elevates Michael's game. Bring her back.

I've grown to hate Pam (and Jim, but to a lesser extent).
It all started when Pam made a play for Jim during the bonfire in Season 4 with Karen sitting right there, and has just gotten worse ever since. I was never the biggest Jam lover, but in the first three seasons their courtship was cute and it made sense. And back when I thought pranks were funny, things like convincing Dwight he was being recruited by the CIA had me rolling on the floor. Now their relationship just depresses the hell out of me. She dropped out of art school to be a receptionist forever so she can marry Jim and live in that depressing house with him quicker? And bitch about the chairs in the office and write passive aggressive notes about microwave cleanliness in the kitchen? It is believable that a person would do those things -- I'll give them that -- but I just don't have it in me to not hate it, especially when she had so much potential for a while. She and Jim are just such unsympathetic losers now, when they used to be the heroes of the show.

All that being said, being funny for five years is no easy feat, so I'll continue to try to take it easy on The Office most of the time. And continue to hope that in two years I'm not writing the same post about 30 Rock. Power of thinking positive, people.