My recollection from interviews is that Dan Harmon and the cast found Chevy just didn’t get the show at all when they were making it. A huge amount of Community’s humour is a mix of meta humour and pop culture references. In the same way that Pierce claimed to never understand what Abed was talking about, Chevy didn’t understand most of what Community was on about - his frame of reference for what is funny hadn’t moved on in decades.

Even though he’s famously a dick, when he says he didn’t think Community was funny, he might actually be telling the truth - not just being petty.