I wont dispute you on any other aspects - except two. have you tried using gevent versus asyncio ? gevent is running in production at several of the largest API services in the world. Asyncio is not yet deployed at this scale.
Second about new libraries being python 3 only - really dispute that. In fact its the other way around. For example, the brand new Tensorflow library (which google uses in production for its own AI) was released on Python 2 only .. and Python 3 support was later patched in. This is the case with every new library of consequence that I'm seeing.