* The desktop icons and click-and-drag shortcuts got removed a few years ago. This is a GUI workflow that I've been using on Windows, MacOS, Atari OS, Amiga OS, going back to the 1980s. Gone.
* They somehow obscured the sleep (or was it the shutdown) button in one version, so that I couldn't find it anymore. I think I had to search the internets for this basic functionality.
* I think one version of Ubuntu GNOME obscured the login screen. I installed it, saw no login screen, clicked everywhere, but nothing happened. Just stared at a desktop wallpaper. If I recall, I eventually figured out that I had to swipe up a little arrow at the bottom of the screen, but using a mouse. Why?
* I think there is still no image preview in their file explorer. I don't know, I don't use it anymore.
These days, I use Ubuntu MATE or Mint MATE, and occasionally drop into Mint Cinnamon to check if they squashed enough little UI bugs for me to use as daily driver. (For example, in the latest Mint Cinnamon, I set my Terminal to 161 columns. But Cinnamon would open the window at Full Screen instead. Oops, back to Mint MATE.)