One thing I miss about the #KDE 1 / #GNOME 1 / #MacOS 9/X days is that there were a zillion different #GUI themes, each with cool and unique looks for widgets. Gradients, drop shadows, brushed metal textures, buttons that look like glass vials full of blue liquid, you name it. GUIs actually looked cool.
Now custom themes, where they exist at all, are nothing but flat, solid, desaturated colors and rounded rectangles. It's dreadfully boring.