Nix does everything I want, but I find it hard to convince friends and coworkers to try out Nix. I think this is partly due to Nix itself not belonging to the Python's ecosystem, so the barrier is higher than say, "Yeah, Pipenv is just Virtualenv+Pip"
Any examples of how Nix itself doesn't do what you need? One example I can think of: Nix doesn't support Windows.
https://nixos.org/nixpkgs/manual/#python