Windows 8.1 was my last version before I made the switch. Windows 8 was horrible. The Metro UI broke all my habits from Windows XP from 7 while also making it harder to tweak my system. By the time 8.1 came out, I'd found enough ways around the main annoyances that its improvements were moot, but many issues remained, such as the bloatware bundled with my PC, and frequent slowness and instability.
As for why I switched, I was attracted by the free software ideal, and trying to get away from Windows, and I had watched and read several things that further convinced me it was superior, but I think the ultimate reason was that I had become hyperfixated on Linux. Thankfully, in this case, autism did not steer me wrong. My level of obsession with Linux has declined, but I still enjoy using my computer much more than I ever did or would on Windows.
I've switched to FreeTube for now, it still works using the Invidious API. This is happening because YouTube is testing forced login to watch videos or use the API. There is a workaround it seems, but we'll have to wait for all the major clients to roll it out.