JS's standard library is smaller than Python's for sure. I... want to say Rust's standard library is as well, but the traits that are present tend to have a looooooot of methods (check out all the methods on Result!).

Python has a lot of things in the standard library, though I think the tendancy has been to stop adding things (case in point: I believe there is very little argument against putting requests into the standard library. I get why they don't but I disagree with the reasoning)

> though I think the tendancy has been to stop adding things

Yep you're right, there's even an official effort to clear some of these out: https://peps.python.org/pep-0594/

Lua?

Lua's use is probably an order of magnitude less than Python or smaller.

Assuming that's even true...And?

You didn't ask about relative usage. You asked for a mainstream languages smaller than Python. Lua almost certainly is.