If I were a violent person, I'd shoot everyone responsible for pushing the flat design epoch. As far as I'm concerned, it's the devolution of stylish, intuitive UI design. I absolutely abhore flat/metro/material UI...unfortunately, abhore isn't even strong enough to convey my disdain. I still use Windows 7 because I'm so passionately against the Win10 GUI, among a slew of other detrimental features and behaviours I disapprove of.
To me, 3D beveled objects and textured or gradient surfaces are far, far more appealing to look at, and much easier to differentiate interactive objects from static space. Even the name "material design" implies skeuomorphism, so "material", in this case, is a misnomer. And you are correct, Andre, I really don't like the "default dark" skin, I don't like any of the v3 skins I've seen so far, they're all flat and/or have hideous color palettes. Give me raised buttons/dials, sunken displays, and colors that complement each other, not contrast.