One fundamental concept we've given up is "what you see is what you get". Open up a window from Windows 95 all the way to Windows 7 and things that behave different look different. The part of the window "inside" and the part of the window border you can click and drag to resize or move around are two different colors. The minimize, maximize, and close buttons are a different color from the part of the title bar you can click to move the window around. Not so anymore. The "close" button is now a visible X and an invisible rectangle around the X. The drag-able border of the window is an invisible radius surrounding the edge of a window. I hope the executive responsible for this rots in hell.

Exactly. Eg. at some point Ubuntu (true also for Win) decided no proper borders around windows and giant title bars. Now I always struggle findig the border, to grab, between two partially overlapping black terminal windows. And wasting screen realestate on title bars and margins just bugs the hell out of me. I've spent hours trying to fix these things, gave up in the end, there was always something that didn't work right. Why did the world forget doing reasonable defaults that just work without tweaking. Oh and don't get me started on disappearing scrollbars, and lazy loading ui components, which reorder what's under focus/mouse/finger every half a second, and make me do a wrong click if I'm in a hurry

      #!/bin/sh
      export GTK_NO_OVERLAY=1

On theming: https://github.com/grassmunk/Chicago95

It works best with Ubuntu Mate. With Ubuntu Gnome it will work but not so integrated.