Comment by sollewitt

You can’t

> partition different applications off from each other, and carefully control how they can communicate.

without

> provide access to hardware resources

That’s still definitely what an OS does. The application model is often very loosely coupled. See web browsers.

A difference between embedded systems and operating systems is the ability to provide access to hardware (in such a way as to isolate and dictate communication) _dynamically_ with a-prior unknown requests.