Maybe I'm wrong but I suspect your parent comment was alluding to that sarcastically.

It didn't fail, it was sabotaged by Synosfky and friends, which then carried on doing exactly the same ideas with COM and C++.

Guess why UWP applications are much slower than regular Win32, app sandboxing and COM reference counting.

But hey, they won.

> it was sabotaged by Synosfky and friends

Is this described anywhere in detail?

Yes, basically when Longhorn started to fail to meet expectations, there were two possible ways, do what Google did with Android, push forward no matter what to make it work, or forcing a rewrite into something else, which is what WinDev ended up doing.

"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...

macOS sandboxes apps, which are usually written in Swift or ObjC and thus use reference counting, and doesn’t suffer from the kind of slowness that plagues UWP. So your hypothesis appears to be incorrect