I sincerely doubt the UIs are getting worse year after year. If that were the case, we would have unusable devices by now. What is really happening is that people are resisting change. The new thing is different---unfamiliar and possibly confusing. That doesn't mean it's worse, but it does mean people will react negatively.
I highly suspect you of being a microsoft employee.
No, really. This is what they believe is going on in people's heads.
YES, the windows UI has been getting worse over time. 98 was an improvement over 95, and 2K was an improvement over 98, but it's all downhill from there.
That being said, the CORE of the operating system has gotten consistently better, with caveats. Vista was more stable, but fucked gaming performance, and performance overall (my HDD light stayed on so constantly I'm surprised it didn't burn out).
Windows 7, our favorite fucking hero, was an unplanned response to Vista hate. It was basically a fixed version of Vista. Vista SP3. UI was good, but bloated, slow, and candy-coated compared to XP.
Windows 8-- more improvements to the core, which users don't see or care about.... and more dookie UI choices. And how many users got tricked into updating to 8.1 by hearing the rumor that 8.1 "fixed" the start menu...?
Windows 10: This is the Idiocracy version of Vista. Shit performance, it spies on you, and puts ads in the start menu. Installs updates whenever it wants (often when you're working).