Python is highly opinionated towards single-threadeding, and the infamous GIL makes "true" multi-threading hard. Async and multi-threading has only recently gotten some love at all in the language and stdlib.

I'd say single-threading is the right call for 99% of Python's use-cases and users. C extensions are available and widely used for core functionality that needs to be fast and/or parallel, e.g. large parts of numpy are in the c extension.