Edit: I just remembered that even Windows was externally acquired, so I believe, it would be more correct to say that Microsoft has basically never innovated something themselves.
Yeah, it started its life as "Quick And Dirty Operating System" (don't know, why they renamed it) and even that was basically a ripoff of CP/M: https://en.wikipedia.org/wiki/86-DOS
I guess, you can say that they did put in own effort into developing the windowing system. I wouldn't want to call that "innovating", since they were late to the party, but I guess, that would be moving the goal posts here...