Is how a story ends all that important? If the end fits the rest of it, then I'm happy.
If the story is good as a whole, I'm happy.
If the end doesn't match the rest, then it doesn't matter what the end is, it might be annoying, but if the rest was good, I'll probably forgive the ending being a bit odd anyway.
If the start, or middle is not great, I'm not so likely to get to the end at all.
In Hollywood movies, there have been cycles of fashion for ending styles. Some years downbeat endings were in vogue, other years it had to be a happy ending. The social climate is blamed, in the case of movies.
Do plaza stories also follow a fashion? Or, is ending dictated by sub-genre?
I think, largely the latter. If you know the sub-genres well enough, you'll see that the ones that fit the pattern have the expected ending, whether that's up, down, weird, twisted, dangling, or whatever.