> Not many projects use setup.py now anyway and pip is still super slow.

Yes, but that's still largely not because of being written in Python. The architecture is really just that bad. Any run of pip that touches the network will end up importing more than 500 modules and a lot of that code will simply not be used.

For example, one of the major dependencies is Rich, which includes things like a 3600-entry mapping of string names to emoji; Rich in turn depends on Pygments which normally includes a bunch of rules for syntax highlighting in dozens of programming languages (but this year they've finished trimming those parts of the vendored Pygments).

Another thing is that pip's cache is an HTTP cache. It literally doesn't know how to access its own package download cache without hitting the network, and it does that access through wrappers that rely on cachecontrol and Requests.