I wasn't trying to undermine their hard work! I think both have a chance of being successful in their own domains. I only meant to call them out as exceptions.
All I was saying is that if a new package manager addresses all of the issues scripting languages had, scripting languages would still use their own package managers. Because the culture is now set, even new scripting languages would write their own package managers.
There's nix-gui: https://github.com/nix-gui/nix-gui
Maybe that's because nix and guix don't interop despite having rather similar principles, and because we mostly don't have GUI for it (like GNOME Software has integration for flatpak) nor desktop integration (like AppImageLauncher). Are you aware of work being done in this space?