When they first fired Harmon I heard that one of the new showrunner was the showrunner of Just Shoot Me. And then they released a press release saying "Don't worry, we'll make the characters just as quirky as they used to be."
That's the real issue with this season. The people making the decisions had no idea why the show was good. They understood what sort of storylines worked in Community, and they understood basically how the characters worked. But they had no idea why it all worked and why it was all funny. The D&D episode wasn't funny because it was a D&D episode, it was funny because the writer of the episode really got
D&D and created an episode that anybody who ever played it identified with. The season 4 crew just didn't get what about the show's subject matter made the audience like it.
I figure the reason they're bringing it back is that most of its viewers are in the big money-spending demographic, and because the ratings underrate the actual viewership because none of the viewers watch it during its actual timeslot.