Microsoft tried that already. It failed miserably. I don't think they gave a reason but I suspect that garbage collection caused too many freezes in early 2000s hardware.
Guess why UWP applications are much slower than regular Win32, app sandboxing and COM reference counting.
But hey, they won.
Is this described anywhere in detail?
"What Really Happened with Vista"
https://hackernoon.com/what-really-happened-with-vista-4ca7f...
"Turning to the past to power Windows’ future: An in-depth look at WinRT"
https://arstechnica.com/features/2012/10/windows-8-and-winrt...