But C/C++ is messy because it doesn’t have a language/platform-provided package-management system, while python actually does.
So that’s apples to no oranges, I guess. And it still doesn’t leave python looking particularly good.
But the Python mess because initially, it didn't have such a system either. Then a bunch of them were introduced, and some of them became official but there was never one that solved all the problems.
I would consider the packages shipped by most distros as platform-provided package-management. It's not specific to C/C++, but if I'm developing something for say, Debian, I'm going to use as many system-provided libs as possible.
Have you tried Conan[1] by chance? I've only used it for small projects, but it was pretty nice.