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I agree with you, but I don't think age or time are the fundamental issue here.
Windows 98 is is 25 years old, and still looks better than almost all Linux desktop environments today, or Linux environments 10 years ago, or 20 years ago. Hell, it looks much better than Windows 10.
In my opinion, the visual appeal of an interface has little to do with age, and everything to do with: consistency, spacing and density, care for detail and, over everything else, good taste.
Sure, today we have a higher "ceiling". i.e. the best possible interface today is better than the best possible interface 30 years ago, thanks to better display technology, better input devices, etc. But we are nowhere near reaching that ceiling. It doesn't matter if my screen has 10 million pixels and can output 8 billion different colors if the UI that I display on it was developed by someone with the aesthetic sense of a 12 year old.