Agreed.
An implementation of a new CPython build system that works on non-current macOS/xcode (whatever version our actual binaries use), a few Linuxes on notably different architectures, and a couple of pesky not-dead-yet BSDs would go a long way toward convincing folks of the benefits of such change. Until that work is done, we’re all just pontificating.
Apparently there is cmake build in the works here:
It seems pretty extensive; I’ll play around with it a bit and try to contact the author.