I don't think Python and C++ are really comparable here. Python was meant to be fairly minimalist from the start. I think if Python "feature froze" right now it'd still remain relevant for a long time. As you mention for its core use case you could argue that it's feature-complete already.

C++ on the other hand was never small. It was never an objective. C++ started as C with classes so it was really just a way to have proper OOP in C. Then it grew and grew and grew, adding more paradigms along the way.

C++ is in a relatively tough spot because it has to maintain backward compatibility all the way back to C89 while at the same time attempt to stay relevant when pitted against Rust, Zig, D and friends. You can't simplify anything because you'd lose backcompat and if you just feature freeze you're doomed to become irrelevant in the not-so-far future.

Unlike Python you can't really argue that C++ as it is now is feature complete. Dependency management is still a nightmare (as is the entire build system really, given that you don't have any standard C++ build system). Concepts are also a great addition to the language IMO that I've been missing for as long as I've used the language.

Coroutines are also fast becoming a standard tool for system programming (for better or worse, but that's a different discussion), and C++'s support in the standard is still experimental.