I really, really, really hate this flatshit design trend. Not so much by the way it looks –or works– but because of the sense of superiority of their proponents. I hate that it is being touted as some kind of movement that is liberating us from the evilness of skeumorphism. It's bullshit. A good designer should put the user experience above his own snobbish idealisms. Function over form.
I don't think its intended as outright superiority, I think its a reaction to it. CSS3 came out and suddenly everywhere everything is rounded corners, gradient colors and shadowed text. It was cool and useful in places, but with the popularization of Bootstrap the internet feels flooded with the concepts. And it did feel like it was pushed into a lot of designs where it wasn't a good fit.
I suspect many people dislike those design choices and are happy to see a counter-push for 'simple' design - flat colors, no gradients, etc.
Don't understand the downvotes, that's exactly what's going on. I alluded to this upthread; this aesthetic is more about Microsoft attempting minimalism to look trendy than than it is about usability, which is why qualified UX folk have been blasting it.