> Meanwhile, the big open-source desktop C++ libraries (Qt and WxWindows) still don't fully take advantage of the types and features in the standard library in 2021.

Of course not. C++ and libraries don't go along nicely. STL is not really useful for cross boundary interop due the fact that C++ ABI is not stable.

Shipping libraries that leak STL types all over the place will only give you headache.