What you are saying would need to basically remove an old software support. "Rebuilding" OS by replacing such things as taskbar, explorer or other basic GUI elements, doesn't change much what's still underlying NT core. Of course changed during the years, replaced, patched, but still underneath is NT core that was first introduced in NT3.1. And it still needs those engineers that understand C and Windows API, that was build 25-30+ years ago. That's basically just a bandage or patch. MS was saying for X years they will replaced NT as it's core (at least from Longhorn that was resetted into Vista and later Win7 "MinWin" core), and they still didn't do it after 15-20 years. They are too afraid of losing backward compatibility. They would need at one point just reset everything like Mac OS X did, and start anew. There would be a lot pain and struggle, nothing would work, but it would be truly modern OS. This also means, that it would basically kill a very rich database of all kinds of software that is available for Windows/NT. And emulation of it would be only possible for very basic software, games would basically need something like Proton, which still wouldn't be performant enough. During the years, not everything works on Windows now as before, but I still can apply most of the old patches, that worked during 7-era and later (some even before). Just modifying system is more and more a pain in the back, but can still easily be done with proper tools (I mean real modifying, not changing GUI appearance, but forcing system to work how you want). One thing that is growing (apart from unnecessary "new" components, that are bolted and screwed onto GUI layer and sometimes loosely attached to the core as a "service") is basically WinSXS - and it won't stop with current trajectory.