The people producing Python or C++ libraries abandon those libraries when they move to a new language - they don't have a choice.
That's certainly true of Python. Hell, you practically need to abandon your Python libraries when you move to the next version of Python.
But it's not true of C++. Binding well-written C++ libraries to other languages sometimes takes a little work (you do need to write a glue layer if there's a serious impedance mismatch, but then you need to do that with C too), but it does work and largely works quite well. Python, Java, Rust, Go, Haskell, O'Caml... you name it, you can The only languages which don't work well with C++ libraries are old languages like Tcl.
Look at LLVM as an instructive example. It's a large complex beast written in heavy C++, but there are bindings for every language you'd ever want to seriously write a compiler in.