Airplanes today have basically the same controls on them -- joystick, foot pedals, etc -- that they did when the Wright Brothers invented the airplane early in the 20th century -- they haven't changed the UI in that amount of time.
Cars haven't basically changed since they removed the manual lever throttle and went with the gas pedal -- many decades of a standard UI.
Why can't we do that with computers? Stop reinventing the wheel!
Do normal people really care about KDE versus GNOME? Don't they just want a UI that works and isn't constantly changing things?
Look at Windows. What are the UI changes between Win95, Win2K, XP, etc. etc. Aren't they just cosmetic BS to make people say, "Gee whiz, they changed X, Y and Z -- isn't that cool?!" Were people really demanding that Microsoft keep rearranging the Control Panel?
What was wrong with the UI standard that every program will have a pull down menu, and on that menu will be a File menu, and in that File menu will be a Close/Exit option, and on every pull down menu will have a Help menu, etc, etc.
The problem with our UIs isn't the UI, it's a lack of standards and a bunch of clueless coders that keep reinventing the wheel and confusing the hell out of 90% of people for no good reason.