John Carmack's arguments against building a custom XR OS at Meta

I'd love a truly new OS, but I just don’t know what it would look like at this point? "New OS" ideas tend to converge on the same trunk.

Building a hobby OS taught me how little is just "software". The CPU sets the rules. Page tables exist because the MMU says so. Syscalls are privilege flips. Task switches are register loads and TLB churn. Drivers are interrupt choreography. The OS to me is just policy wrapped around fixed machinery.

try to quickly spawn a lot of processes on windows

I think any OS can be divided into a "backend" that deals with the hardware and a "frontend" user-level applications with a UI. The backend is mostly similar everywhere, while the frontend is what the general public typically perceives as the "OS". It's hard to see anything truly new in the "invisible" backend, but the frontend changes with every update (Windows, Mac, Linux etc). ACPU OS is a good example of this, where the backend can be a different OS, an emulator or actual hardware, while the frontend remains the same across all execution environments. https://www.acpul.org/blog/so-fast