Maybe you have to see it to understand, because I don’t understand this argument at all. What is it about a flat rectangle that benefits from retina? If anything, I would think textures would benefit from retina.
Now, on HiDPI displays we can go back to using more detailed fonts that we use in print without loss of quality, so the text part of the interface gains a lot in aesthetics and character, so much so that we no longer need all the stuff around the text to make it look good.
Additionally, because HiDPI displays are able to show that much more detail, it is a lot more difficult for designers to create skeuomorphic interfaces that look believable. The crudeness of the old displays helped mask the simplicity and lack of realism of the skeuomorphic design. Our eyes and mind knew that what was being represented is not real, just an impression, and so we evaluate it as an impression, not as something real. On contrast, HiDPI resolution is so high that what's being represented actually looks real, but if the smaller detail is off the effect of realism is lost, so the overall thing ends up looking like a poor fake rather than a good impression.