Well you certainly do your homework. I read a few of those posts, and I appreciate that some intelligent discussion is happening, but what I did't see is people discussing effort. What I mean by that is the new flat icons take little or no effort to create. For example I am not a graphics artist but I am quite sure I could reproduce the 10.10 Mission Control icon in under an hour, easily. The 10.9 version would be tough.
If you study art you'll learn that a societies art represents what they valued at that time. Icons, fonts, the UI are computer art in my mind, I think Jobs was a last hold out for really good art.
On a broader scale, simplification, its so pervasive these days. For example, when I visited Crissy Field in San Francisco, seeing the Mark di Suvero exhibit, it looked like someone dumped there construction waste (I was terrified it would be permanent). People tell me beauty is in the eye of the beholder, but doesn't the effort and skill involved mean anything? If you're impressed by big girders, go look at the Golden Gate Bridge to satisfy that desire, that's beauty and function!
Apple proved that people will pay for quality, and ascetically pleasing machines, they were the underdog for a long time but they didn't give up that vision. I think people recognize quality and beauty and the "effort" it takes to build it.
Apple was "Liberal Arts plus Technology", is Apple joining the rest of society, or the industry in general were colored squares are good enough?