If you think iOS 7/8/9 are hard to use, try Windows Phone 8. I had a Lumia 620 for a while and it was pretty hard to understand what was going on for some applications (aside from the fact that their back button behavior was something that was completely confusing). It's odd too because some of the non-Microsoft WP8 apps were very easy to use by comparison, but the Microsoft designed apps were the worse in terms of usability for me. So, I'm not sure if its the design aesthetics at play here or maybe just that some developers are better are conveying what certain UI elements do and what to expect from them. Either way, I think there has to be a middle ground between removing clutter from UI and avoiding what amounts to snow blindness for computers. In my opinion, the Material Design spec by Google is closer to the sweet spot than what I've seen so far (I think it needs more UI hinting of some kind and less empty space which makes it harder for me to focus on what's going on in an app).