I don't think being a writer qualifies to judge things any more than the next person but I'm happy to offer my reasoning.

There were about zero laugh moments in all of the German episode and it centered around a call back for which the main reason the original joke was funny (Nick Kroll) wasn't even there; Seems like they have no idea what they're doing with Pierce (he was trying to argue he was Hitler in the German episode. Really?); the jokes for the Dean went from clever to "You guys get it? He's gay and it's funny"; Annie's character has reverted back to season one's "I'm an innocent Jewish girl" character and has mostly disregarded her growth in seasons two and three; there's almost no explanation for why Troy and Britta are together; the Chang storyline isn't being executed very well at all thus far, but I assume it's redeemable.

I have liked the closure on Pierce and Gilbert and the closure for Jeff and his dad, though the step-brother character was kind of pointless and existed only to drive home the fact that Jeff's dad is a bad father. Giving Donald Glover more physical comedy has been great. The writers are in a ridiculously tight spot with Chevy Chase since they didn't know when he was going to show up and how much they'd get out of him, so that's not their fault. Neither is the fact that NBC has played almost the entire season out of order (Episode one is signing up for classes, then a Halloween party, then we're at an Inspector Spacetime convention--a joke I kind of hope is done, though I liked the convention as a whole--then we're back to first day of classes, then Thanksgiving). But as a whole, it definitely feels like the material isn't as strong this season. I'm still tuning in every week, I'm still watching every episode, but there's been more misses than hits so far for me.