Was season 4 terrible? No, it had its moments that were decent, but it is definitely the worst season. Not having Dan Harmon definitely negatively affected the show. I think part of the problem is they tried too hard to bring back the past (darkest timeline, paintball) or veered too far from what makes Community great (Economics of Marine Biology, Conventions of Space and Time) that it did not feel like an episode of Community. Those two episodes lacked the smart wit that one came to expect from the show (this was also kind of true for History 101, though I get what they were going for in that one). I think some of the things that were brought over from past seasons worked well (the puppet episode was quite good IMO), but a lot of it just felt forced, especially this episode. There were episodes that worked though, specifically Intro to Knots, Basic Human Anatomy, and Heroic Origins. Each felt like an episode of Community, but they did not seem like a ripoff of a Dan Harmon idea like Advanced Documentary Filmmaking or the aforementioned bits about the darkest timeline and paintball. Some episodes just felt a little flat to me (Alternative History of the German Invasion and Cooperative Escapism in Familial Relations). Overall, it was not a terrible season, and a few episodes hold up well to a rewatch (episodes 10-12 being the best) and would not seem out of place in seasons 1-3, but it just did not have the same witty humor and fresh feel of other seasons of the show prior to this season.