I wouldn't call it eye candy, exactly, but I do think that most HN design submissions are little more than illustration. But I also think that design is much more closely related to engineering than any primarily superficial discipline. (Such is my experience after an undergraduate in physics and a master's in architecture.)

Both engineering and design are instances of the same type of problem solving process. But because design is focused more on qualitative and subjective elements, its state space is much larger and, I believe, its design solutions (or attractors) more fuzzy. Because of this, design and engineering actualize themselves quite differently in real life, often requiring different skill-sets.

And I think that because the web and application design disciplines require more engineering-thinking -- architecture, for example, must also consider spatio-temporal qualities -- most design-thinking is delegated only to the most superficial facets of the process. What would really help understanding is for more designers to push into the engineering side of things, and more engineers into the design side of things.