I missed the boat on Community, and after catching a few episodes in syndication, I binged my way through all four seasons before the fifth season premier.
For the first three episodes of season 4, I was confused as to why people hated this season. It had a few awkward moments, but so had all the early episodes of other seasons. What was the problem?
As I went on in the season, though, I started to figure out what the issue is: this isn't a "season" in the Community sense. Seasons 1-3 had always had an arc, the story gradually building to a climax, with shifts in the status quo. Season 4 was not doing this. Season 4 was introducing ideas, forgetting about them or not developing them enough. Season 4 didn't build to anything. Season 4 was an assemblage of episodes. Some of them are good, some of them are not, but it didn't add up to a whole the way prior seasons had.
This also meant that characterization suffered. Most characters continued on at the same level they were at the end of season 3, without changing or growing. The exception to this rule was Pierce, who, episode 8 aside, backslid into where he was in season 2. If I were Chevy Chase, I'd have quit too.
So of this mess, what's worth watching? I really liked the first 3 episodes. Jeff's story in episode 5 is good material, though the B-plot is weak. Episode 8 has the best moments for Pierce in the season, and it's a shame that Rachel is forgotten as soon as she's introduced. Episodes 10 and 11 are also good, though the fact that Troy and Britta relationship wasn't mentioned for so long makes it an underwhelming end to that non-arc. Still, Jim Rash channeling Joel Mc Hale is one of the funniest things to have ever happened in the show, so don't miss that. And the season finale, while a little corny, is also a lot of fun.
Be sure to avoid "Intro to Felt Surrogacy," the only episode to be truly terrible (though YMMV). The rest are just mediocre, and the series' refusal to develop story arcs means that they can be skipped.
In short, I'm glad that Dan Harmon didn't completely wipe this season out of existence, because it had some good moments, but I'm definitely glad he's back. The fifth season already taking more risks and aiming higher than season 4 did, and hopefully will restore Community back to be great, rather than just "pretty good."