Microsoft has been going downhill for a loooong time, the stupid Ribbon Bar drove me off of MS Office 15+ years ago. The control panel in Windows XP was a mess and it's only gotten worse as far as I can tell.
I do blame monopolies for this in part. When some single thing dominates (office suite, web browser, whatever it is) the comparator shifts. It's no longer "how do these 6 things compare", it's "is what's new here entertaining enough and not too much of an inconvenience to cause me the pain of abandoning an entrenched tool?" So then users convince themselves the improvements are progress because it's always implicitly compared to the alternative of struggling against the lack of choice of other products.
That's not all of it by any means, but I do think it created a context for what's deemed acceptable ux-wise.
MacOS isn't all it's cracked up to be though and is maybe another historical source of this mess. I use osx daily and it's much, much, much too easy to lose track of open windows. Dialogs open and you don't even know they're there, and you find windows open that you thought were closed weeks ago.
This doesn't happen with a lot of other OSs, or at least used to not happen.
My favorite UX has always been through KDE, although I haven't had the opportunity to as much as I used to because of work reasons.