The most critical useless feature (as it is now) is actually the Windows Store. What is Microsoft doing wrong that makes nobody use it? It could be a revolution (selling + updates).
In Windows 8, the Store and the not very good WinRT apps launched together. If they had launched with support for Win32 maybe it could have gotten traction. All your favorite desktop apps could be updated in a fell swoop without leaving junk on the system tray, extra updater services, or prompting you. But they assumed that WinRT would be successful and have popular apps, and instead what they got was a store to inst…
- Firefox - office suite (Libre Office for me, Office for my wife) - games (Steam) - backup software - video chat - image/video editing
Some of these could work just fine with WinRt, others don't. If most of my frequently used programs aren't available through a store, I'll complain about the store. If most are and a couple aren't, I'll complain about those apps.
Most apps people want don't currently use WinRT (AFAIK), and many apps probably will never use it (heavy software like games, maya/blender, photoshop/gimp, etc). It's really telling that Microsoft's motivations are when they prioritize the least used platform (and the most beneficial to Microsoft) in a new app store.