This is a joke from Community about open ended TV shows typically having enough narrative steam to get a compelling run of six seasons and a movie at best. Not a financial thing.
Community has crawled through the trenches to get its six seasons and now finally a movie and I wish them the best.
I wasn't thinking of it as a Community joke, but rather a Dan Harmon quote/meme that he placed in Community (he's nothing if not meta). If my memory is correct (and it does get a bit fuzzy over time), my comment above is paraphrasing him or some other explanation of the saying.
Sometimes shows naturally have a 1 or 2 season arc and sometimes (rarely) they go out strong at 6 or 7. But, yeah, for me sometime around season 5--even if a show has successfully mixed things up a bit--I find tuning in for new episodes more and more optional in most cases.
Community has crawled through the trenches to get its six seasons and now finally a movie and I wish them the best.