I personally like Quart, which is like Flask, but with asyncio. Django is also incredibly popular and has been around forever, so it is very battle-tested.
I've been using FastAPI which is made by the same guy as Flask but taking it seriously this time and using asyncio and making space for multithreaded. It's almost a drop-in replacement for Flask.
I started with cherrypy, then used twisted for years and finally aiohttp made me never look back or search for anything else.