Legit question. ChatGPT isn't super helpful here since it agrees with everything when I'm really looking for someone to say why this isn't really feasible in the real world.
This is at least true for Windows and most traditional (X11 at least) *nix systems.
That is one thing I think Android got right... by default it runs every application as a different user. That means different home folders and no visibility into other apps.
Permissions are difficult to get right, and Android is unfortunately pretty slow to react.