The problem is the GUI. People don't like X
Non-sequiteur. X has nothing to do with the GUI, at least not any part of the GUI users care about. X is merely the tool used to draw stuff on the screen; it says nothing about what gets drawn. Everything users care about, including what windows, buttons, fonts, etc., look like, how applications interact with one another, and whether or not all of the above is nicely integrated and looks like it belongs together has nothing to do with X.