I might be getting confused here (I'm a casual fan, not a Dr Who expert) but I think I have an idea:
He's the writers who's made the series much 더 많이 complex. Before, 당신 had mostly episodic plots with one story running through a series. Now, 당신 have story lines lasting for 2 또는 even 3 series. I think some people miss the old format. Also, this new format can be confusing for casual 팬 (like myself, but I don't personally hate Moffat for it), since they don't rewatch episodes enough to remember every detail.
I don't hate him I feel he has made the show better. Most hate him because he came 초 he changed the show up and made it 더 많이 harder to follow. Also most 팬 that hate him loved the 10th doctor so he left just about when Moffat took over. Also people feel he is sexiest.