I try every year I try a few different Linux distros and each time I notice a tonne of UI and UX issues, and leave again (I mean, even the basic things like being able to resize windows is 95% of the time a pain on most distros I try. I'm sure there is a fix for it, but the point is, you shouldn't need to fix it, it should "just work").
In my mind Ubuntu is the closest, but still far far away.
I love Linux, and I use it almost every day (Debian), but only ever as GUIless servers, which it's amazing at.
Just hope one day a team with design and ease of use will make a distro that "normal" people can enjoy to use. (but you would need other apps that look and work great in it too, which I fear will be the harder issue to tackle)