On the topic of flat design specifically, developers are likely just as culpable. Back when it was just starting to catch on, by my observation some of the quickest to adopt it were solo developers because it's way easier to build a passable looking app with flat UI since that doesn't require any design talent.
That looks perfectly functional to me? It only looks a bit ugly because the screenshot appears to have been of a very small part of the screen that got blurry when it was blown up to a larger size.
I'll take function over for every day. (I daily drive KDE, it works fine and doesn't get in my way. Most of the time I'm either in my editor or the terminal emulator anyway.)
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