In my opinion the UI of Windows 10 worse than either Windows 7 or 8. While Windows 8 was like running a modal OS - one mode for desktop, another for tablet - Windows 10 doubles down by awkwardly gluing these interaction modes together and making both worse for it. That's not to mention the overall sloppiness of some aspects of Windows 10 like mismatched icons/windows/settings, etc.

I was not a fan of Windows 8, but Windows 10 is worse! I'm not sure which users they were catering to in this regard.