This is an industry-wide problem, not exclusive to Microsoft. I feel like everyone has just outsourced QA to users. There's been a drastic decline in software quality at release, particularly in the past year-year and a half.
Initially I thought maybe it was just getting difficult to maintain these behemoth platforms that have been around since the 90s but it's infected the gaming industry as well, total green field projects where you can expect the v1.0 release to be almost unusable until 1.1 or 1.2+
I think a lot of it has to do with how little software -- even enterprise software -- is actually written from the ground up. Reliance on both external libraries and modules owned by unrelated internal teams has made a lot of both the programming and debugging almost black box, where effective testing isn't really tractable.