Windows 2000 was the last system in the world with coherent and beautiful UI.
Those times are over. We can't have good things.
I concur that I’m not a fan of modern UI/UX, though. Give me the interfaces and the UI guidelines of Mac OS 8, Windows 2000, and Mac OS X Tiger (with Spotlight) any day.
Tiger’s Aqua comes in second, and Leopard/Snow Leopard’s third. I never really liked the ubiquitous dark grays found in 10.5/10.6, it felt kinda gloomy in the same way Win95/98 did relative to Win2K (also due to darker grays).
A couple examples I picked off the XFCE screenshots page:
Linux need some visionary company which will push hard on some sane technical choices without alternatives to provide coherent vision. It would require tremendous resources and it'll cause tremendous resistance from community (just observe how much hate systemd receives and it's still not as convenient as services.msc from Windows 2000). It's unlikely to happen, so that's why I think we won't have good things, because Windows itself lost its vision as well.
Aero, or at least the slightly toned down Windows 7 version of it was better than Luna, but similarly to me the bigger benefit it brought was the more capable theme engine. There were a lot of awesome third party .msstyles for it too.
I’ll forever resent Windows 8 for ripping out that nice theme engine in favor of one barely more capable than what shipped in Windows 1.x.