And Mavericks was the peak of GUI look-and-feel, before they went with the all-flat look.

The flat look is good, but the regression in UX is not

I really loved Aqua (especially without the pinstripe backgrounds)

The flat look and feel is exactly that.

This. Double tap dragging felt great. I don't understand why they killed it. BTT revived it. They killed it too :) Why? \(??)/