I agree completely.
Look at Plan 9, if you haven't. I can open a window, add/remove things from its environment (via mounting and unmounting files into that window's namespace) seal that environment to prevent changes, then launch a program.
The program can only see what is available to it via the file system. If it has no /net folder then it can't talk to the network. At all. If it has a truncated /env then it can only see a subset of the environment variables available to me, the user.
EVERYTHING being a file is ... weird. Unix has that, but Plan 9 takes about as far as it can go, which is pretty far. But that makes permissions to things quite easy, because file permissions are easy.
The other thing that Plan 9 does is that everything is a file, including your environment, mounting and unmounting things from/to your environment is how you gain/deny access to yourself and to programs.
If this permissions model was common, ransomware would have never been possible. No virus could infect your system, only its own environment (with caveats).
If you already know all of this, I apologize. If you don't, then you owe it to yourself to have a look at Plan 9. It's very weird, but once you wrap your head around it, you start seeing why some people really rave about it.
There's a channel on YouTube called "adventuresin9"[0] which has TONS of content about Plan9.