Let me preface by saying that unlike many others here, I'm using windows on purpose, on my main machine, because I like it, and that since W95. And I'm still using it right now. I like how it's in a sort of spot between great customized but closed down experience of OSX, and completely open but very messy even today of Linux.
But for a long time, Windows struggled with some broken internals and screwed up stuff, drivers would destroy your computers randomly, security was essentially not a thing, virus and rootkit were more common than normal applications, the works.
Microsoft did a lot of great advance on that, Vista brought the great internals revamp, 7 cleaned it up and made it usable, ... But that's when they started having some "finished" part and let some idiot ruin them.
8 kept improving the internals, but the interface and settings were already fine so they let someone make it look and feel like a tablet OS, and a broken one at that. Then tried to hide it with 8.1, but the damage was done.
10 was, for me, the best Windows version; but with all the internals polished they now decided to add a veneer of crap on top, let's track users and install candy crush for them.
11 ... I have no idea what's happening. Forget the "apps like on phone" start menu brought by 8, now it's not even that good, also here are ads in it. The contextual menu is broken beyond belief, but there is a button to show the real working one. Changing browsers ? Oh no, people need to change the HTTP handler now ! And half of the stuff will ignore it and force-open edge anyway.
Microsoft was doing so much better with Windows when part of it was broken. They were working on fixing it. Since it's been done, they're now in the business of adding and changing parts of it just for the sake of it, and effectively breaking everything in the process.
Add to that, it was great for Microsoft the company to diversify away from Windows in revenue, but that lead them to consider it just one of their toys. They're doing to it what they did to Skype.