When I first started out, I used to customize my system constantly. Then I switched to KDE Plasma, and aside from a few minor configs, I’m completely satisfied with Breeze.

The X Window System (aka X.Org or X11) has been the default window system in many distros. Recently there has been a new window system called Wayland, so the joke would be that Debian is dropping X11 and switching to Wayland.