Consider also that basically every single ground up "we are rethinking everything, and doing it right this time" OS rebuild from scratch has been a failure. There have been dozens, if not hundreds of examples.

https://en.wikipedia.org/wiki/Second-system_effect

https://en.wikipedia.org/wiki/OS/2

https://en.wikipedia.org/wiki/Plan_9_from_Bell_Labs

https://en.wikipedia.org/wiki/Copland_(operating_system)

https://en.wikipedia.org/wiki/Windows_Vista#Development_rese...

https://en.wikipedia.org/wiki/Cairo_(operating_system)

https://en.wikipedia.org/wiki/Multiuser_DOS

https://en.wikipedia.org/wiki/GNU_Hurd

https://en.wikipedia.org/wiki/BeOS

https://en.wikipedia.org/wiki/Singularity_(operating_system)