They gutted QA in 2014, ending their software development engineer in test positions, and suggesting the developers should test their own code to get velocity.
Subsequent releases were worse than before, and things have compounded since then. Hard to say that laying off the rest of the team made a noticable difference.
Blame Satya Nadella. He fired testers and turned customers to helpless beta testers.
QA doesn't get enough love :(
I've edited my comment to correct this. Cheers!
But according to the other replies, it seems Microsoft has been purging QA for years now.