I've been very hard on Flat UI in the past (and still dislike the overdone blocky look) but I've decided to embrace it after realizing it's true purpose.

It's NOT to destroy skeuomorphism. It's to destroy "forced focus design" in favor of "distraction free design". In the past we used gradients to aim the eyes towards a direction, shadows to make elements pop out of the page at a viewer, overly rounded corners to seem friendlier to the viewer, etc... We styled elements like this so we could draw attention to certain things and away from others. The same way people wear certain clothing to stand out or fade in with the crowd.

However, in this era of instant gratification online property owners not only realized that content is king but that there's too much shit to do and not enough time to do it. They need to give the viewer what they want and give it to as quickly as possible. Confusion breads negative feelings and pissed off viewers leave and don't return. So pages became lighter, more minimal, and lost unnecessary elements, and so designers adjusted to this.

By getting rid of the un-needed information on a page we no longer have to draw attention to one thing and away from the other because everything on the page is important. If it wasn't, it shouldn't be there in there in the first place. The buttons don't all need to have massive rounded corners and huge shadows because they're no longer lost in a sea of text and ads. They're easy to spot.

This is why you'll notice a lot of Flat UI sites are a lot more minimal than usual.

The Flat UI that I HATE is the blocky kind. Minecraft / 8-bit / designer out of college / what the hell's an a/b test inspired extreme flat ui. The kind where you don't know if that's a header with a colored background or a clickable button. The flat ui where everything on the site is so white white white you'd think the owners were clansman. That crap I hate. And it's only a few dozen A/B tests away from disappearing off of prominent sites.

I don't think this is "just a fad" anymore. There's a reason big companies are switching to it. Microsoft, Apple, Google. They're not stupid. They run A/B tests. They're not going to sacrifice market share, page views, usability, ease-of-use, and their bottom line just to blindly follow a design fad. That's just an insult to them. To say all Flat UI is backwards while the internet's biggest companies convert to it just goes to show how delusional and unknowledgeable we (especially I) can be. I apologize for my past remarks.