You think no one cares about the convenience of having the type system do a lot of the work for you? Or being able to autogenerate client libraries? I find that position confusing.

Proper async support is decently important to me in any language or framework, but in the real world, I haven't often run into other developers who care much about that.

Async in Python is a huge deal as it is in any language, yes. For very real reasons (cutting down on incredible amounts of confusing boilerplate) to very lame reasons (it's been memed into developer consciousness enough that it becomes a primary yes/no gate for development teams).

I assure you, a large part of using fastapi for my company was the integration with pydantic for easy validation.