FWIW, I've waited literally my whole life for computer graphics to get so good that people could make photographic quality icons - not to squander modern technology to draw 1970s era monochrome vector line drawings. For my preferences, the most beautiful OS-X was Tiger, and the prettiest iOS was iOS 6. (Not to imply that there was nothing great since then - many Tiger/iOS elements were preserved.)
Why on earth would you want to make icons look like buttons on a platform where you don't press them? Why not make the OS itself a thing of beauty to be proud of, instead of something that fades into the background? Remember how people pay 10x for Apple laptops - it's a luxury device. And the look of the OS is part of that luxury experience.
I realize a ton of you folks love the idea that icons should be just a few simple lines, but I wanted to post this to represent the people that appreciate graphical richness.
That being said, I'm way waaaayyyyy past being "horrified" by Apple making bad graphical choices. I'm more concerned with functionality. Like when Ives decided that icons in the finder pane should all be black and white, and all of a sudden, I couldn't easily spot my shortcuts anymore. That really hurt my productivity as well as aesthetics.