First, the privacy violations unfortunately started around that time. It used to be less bad than now, but Windows 8.1 brought things like an advertising ID and location data. Mandatory telemetry was not originally included, but Windows 7 and later have received this spyware with updates.
Windows 8.1 brought a lot of improvements, but it’s still hampered by the basics of Windows 8. And a lot of functionality is still in apps, like Windows 8, that are designed for tablets. You still have the charms bar, for example, where a number of settings options that you won’t find on the desktop are hidden away.
With Windows 10, they put both worlds together pretty well in my opinion with Tablet Mode. I think that’s what 8.1 really needed, but I don’t think they could have done it as a minor update. In fact, I think the 8.1 has a better tablet interface than the 10.
My experience with 8.1 is that it is an “8 with patches”. There were a lot of good things in 8.1 as well, but the patchy attempt to drag settings and apps from Win32 to UWP that didn’t really start showing up until Windows 11 makes it a very frustrating system for me.
The user interface is a pity, because the kernel has improved a lot after Windows 7. Hyper-V, better driver templates, more stable graphics APIs, and virtualization-based security Windows has really improved greatly. A great piece of software ruined by designers (who all had Macbooks themselves) and thirsty for data.