The show doesn't really start taking off until the end of season 1 when it starts to get a bunch of highly rated episodes
However, if you are already on episode 12 and not liking it, IMO you aren't going to like the rest of it.
Guessing that chart mixes up season 3 episode 3 & 4 because 3-3 (Remedial Chaos Theory) is widely considered one of the best episodes of the whole series and possibly THE best episode.
Maybe I should give season 5 another try, but I found it overall really bad. Season 4 was bad because it was boring and didn't feel like Community. Season 5 was bad because it felt like an exaggeration of Community, like someone trying to relive their high school days during a mid-life crisis. Some of the episodes have fun ideas, but the execution is off. Losing Chevy Chase was no big loss, but losing Troy a few episodes in was devastating to the cast dynamic. With Troy's enthusiasm gone and the new cast member being a bitter, old man, the season just feels mean-spirited.
Season 6, on the other hand, felt like a cross between the more grounded season 1 & the highs of seasons 2 & 3. The two new cast members are great additions and Keith David & Paget Brewster threaten the steal the scene every time they're on screen. I get that season 6 has a very different feel than the past seasons so it won't be to everyone's taste, but it really reinvigorated my love for the show after the lows of season 4 & 5.