Highly controversial opinion: around the time quality seemed to very noticeably take a nosedive (Win8?) was also roughly the time all the "diversity and inclusion", "anti-meritocracy" etc. stuff took off. Maybe we are just seeing the proof of what happens when you hire people for who they are rather than what they can do.

Someone in another comment here mentions Raymond Chen. He is from the "old Microsoft", and probably has significantly less power than he used to.