No idea what a Windows app looks like, though, I recently fixed my grandfather's Windows 8 laptop and immediately gave up trying to understand how theming is meant to work.
I now focus on making my shell/terminal environment as good as possible and ignore GUI land whenever possible. Which today pretty much means 99% of the time I'm running a bunch of terminals and a couple web browsers.
But beyond that, it's a mirror of the graphical side. I mean, it's not like the GUI invented a lot of new widgets, either. There are still buttons and menus, it's just that they look and behave differently in each app. The same goes for the CLIs, where there's no rhyme or reason for all the long/short parameters, sub-commands etc.; To use the git metaphor, we're in a bathroom where all the porcelain is coming from different manufacturers and your got your brutalist toilet bowl next to your gold plated sink. And nobody knows what to do with the three shells.