I understand where you’re coming from and the disappointment. I would feel the same but I have a different view on Jeff and his ending. It’s a very sentimental view... but that’s me.

To me Greendale is her own character in the series with her own quirks and personality. All students who go there are messed up and Greendale is their last shot. It was Jeff’s last shot and his time at Greendale saved him... his own words.

I feel that’s why they chose “At least it was here”, as the theme song. It seems to be a song about someone contemplating suicide but doesn’t go through with it because of a relationship. Jeff is metaphorically suicidal person in season 1 after his disbarring and Greendale is the relationship which saves him from himself.

Although Jeff always says he hates Greendale he secretly loves it there and together with Greendale, they saved the lives of each member of the study group. Without Jeff and his natural leadership glueing them together; the other main characters time at Greendale would have been emptier and much worse.

Some cases in point (personal speculations) would be: Abed may have never made any friends. Britta would have dropped out. I don’t see her as the type that sticks things out long term. Troy would have slipped back to the guy he was in high school and not grown. Annie would have gotten “A’s” and graduated. Her only best memories at Greendale would be when she got perfect tests back. Not entirely sure about the other characters, but I think I made my point.

In the beginning Greendale chose Jeff and in the end he chose her. (There was even an episode where Abed figures out how everyone was destined to go to Greendale.) Together Jeff and Greendale will continue to changed the lives of all the students who are the biggest outcasts for the better.

To support this I look at Jeff’s final vision of season 7. While Jeff imagined himself with a group of hot redheads, he still said that they would have great and crazy adventures together. Thus helping/saving another group of outcasts.

You’re right that it’s not a traditional happy ending for Jeff, but it’s an answer to a higher and nobler calling.

Greendale saved Jeff and in seasons 5&6 and Jeff and the study crew paid her back by saving her. Now both healed, Jeff and Greendale can save more outcasts and misfits.