I disagree. They're no worse than before. The reason for any bugs slipping in are because of the vast diversity they need to support in the PC eco-system. It's substantially easier to producer higher quality software when you only support 3 to 5 standard configurations.
My experience contradicts this ( for the little that is what is worth ). Vista, W7 and W8 were all comparatively stable (loved windows8 as a reskin of w7 with much smoother performance). Service pack- grade updates never broke the system or made features non functional.
Maybe some of the bad taste in my mouth comes also from trying out insider builds at one time (for both W10 on PC and on the phone). Thouse were also terible. I'll forever remember the Groove player for phones which could only play *some* of the mp3 files (about 2 thirds !), in 2016
The start menu refusing to show itself is an issue that spanned multiple bianual updates (it'd be nice if it really was fixed for 1809).
The other huge problems are the silent failures of File History (which would be the kind of functionality one would rely on). And then the unreliability & slowness of modern apps. Calculator (e.g.) takes some 3-4 seconds to load on my 7980XE. That's when it works.. sometimes (often!) launching it results in an empty window that needs to be closed and hopefully the next time it would actually work.