This isn't supposed to replace Windows, and it isn't a GUI desktop operating system at all. I doubt anyone working on this has anything to do with the modern Windows desktop UX.

> This isn't supposed to replace Windows,

OP wasn't suggesting it was, just that the lack of quality in one significant area of the company's output leads to a lack of confidence in other products that they release.

but if the host OS is already comprised, what is the point of sandbox inside of it?

Maybe we need secure attestation for sandbox to be protected against compromised host :)

It does sound hard, and might need to employ homomorphic encryption with hw help for any memory access after code has been also verifiably unaltered through (uncompromised) hw attestation.