You can't even use it without the documentation of the program that you want to install because some dependencies have to be installed manually, and even then there's a chance of the installation not working because a unit test would fail.
the only time i've had issues with pip is when using it to install the xonsh shell, but that's not really pip's fault since that's a very niche case and i wouldn't expect any language's package manager to handle installing something so fundamental anyways.
Getting into rust is still on my to-do list, otherwise I've no major problem with pip or npm. They both have their flaws, but both work well enough to do what I need them for. If I had to prefer one it would be pip simply to sustain my passionate hate for all things JavaScript.