This is probably quite unpopular, seeing as the FastAPI docs have been so praised in the past... but I really dislike how FastAPI is documented, which has really put me off of the project.

The FastAPI docs read like a full project, a very dense project. Sometimes you just want to learn about a specific feature, but you walk into a page that assumes you have the context of the previous chapters, that puts me off a lot.

I also dislike how some of the documentation is absolutely enormous (the SQL chapters is one example), but I suspect this might have to do with the not-so-simple approach FastAPI takes, as opposed to Flask, which is indeed very simple.

I really can't join the crowd here. I don't think FastAPI is a replacement for Flask, even when async is taken out of the equation. Flask has some weird quirks to it (like "g"), but it really is a beautiful and simple API for the web.