I feel like I'm one of the few people who still likes flat designs. I hope it doesn't swing all the way back to full skeumorphism. YouTube looks way better than it did five years ago. What I do miss is efficient use of space. HackerNews still has a great design, it's really efficient with space. Old school iOS used space efficiently too, because it had to. It only had a 3.5" screen to work with. I miss that.
What I miss since iOS 7 is buttons that look like buttons. BUTTONS THAT LOOK LIKE BUTTONS. Is that too much to ask!?! Why are we stuck with sometimes plain blue text, especially when the use of that blue in UI "elements" isn't even consistent with regards to function or behaviour.
As a user, I like where flat design has taken us, generally. But I absolutely agree with you: the loss of “functionality hinting” (I’m sure there’s an actual term for this, but I don’t know what it is) is pretty bad. You can stumble around a design that isn’t in your language, if the cues are strong enough. But all-text directions throw that right out.