For that matter, one could for example take the Windows NT 4.0 source code, add in drivers for the necessary hardware, fix boot code, linking, etc to be compatible with late model computers, spruce up the UI with better font rendering, antialiasing, 24-bit color wallpaper, OpenGL rendering even--and in the end, you'd have something just as functional as Win 7/10 but at 1/4 of the bloat.

This sort of thing would be technically very easy to do. It's much easier than the status quo of continually reinventing the wheel. So why, oh why, is there this overpowering desire to continually throw out good code and replace it with heavier, more bloated junk, which doesn't really offer any real increase in functionality?