I assume Microsoft would be able to rewrite the monolithic Windows kernel to a microkernel. So far, they haven't but it wouldn't surprise me if they experiment

I assume Microsoft would be able to rewrite the monolithic Windows kernel to a microkernel. So far, they haven't but it wouldn't surprise me if they experiment on Azure with a custom microkernel version of Windows. Linus Torvalds is a strong proponent of monolithic kernels so I don't see him changing his mind.