I doubt they are even capable of adding good security. Windows' hiostory up to wMe in short form: added more and more rudimentary layers onto the (pirated?) DOS operating system. for Windows NT: employed a bunch of excellent VMS OS designers, let them create a nice system core and add a lot of old bloated DOS/WIndows code to it for backwards compatibility. XP: take NT and add more backwards compatibility bloat.
Noone has enough resources to clean that up and make money at the same time.
backwards compatibility is a good thing... Microsoft went the wrong way: bloating. Apple went the right way: emulation, as in Classic mode, Rosetta...
Microsoft haven't made a good product by the standard of the age since Windows NT 3.5 (well, I might be exadurating)