With my "reservations" about Microsoft, I do credit them with maintaining very good backward compatibility.

As I remember it with Vista, some Microsoft insiders indicated the overall design was so complex and deep that no single person on the team actually understood it. Thus, they said, a lot of inconsistencies appeared. Within the time and development budget, all they could do was superficially patch and hope.

On a positive note: I think Windows 10 gets it right -- finally. At least based on my usage and reading. This does not mean they got it "perfect" as Windows 10 is too complex for humans to get "perfect".

Windows 53 will probably be perfect as it will be developed by sentient-AI, not people.