It's possible to make something that looks... utilitarian for lack of a better word, but that still looks good. The Millenium Falcon is a perfect example of a ship that looks crappy, but everyone still loves it.The K Wing is the result of an undisciplined and uncontrolled creative mind. It misses the aesthetic ideals of the other fighters and I don't mean in an in-universe kind of way, I mean from an artistic development kind of way. When something HAS to look a certain way, like the Lancaster or the A-10 mentioned above, then all is forgiven in terms of appearance. When you're dealing with a purely fictional ship, then form is much more important than function because function effectively doesn't exist. As an artistic choice, mimicking the 'form over function' appearance of certain real-world military vehicles is fine, but only if you hit the nail on the head. It's such a narrow target to hit, and if you miss it you wind up with a ship, like the K Wing, that just looks silly.
Fiction or nonfiction doesn't really matter in my opinion.
Having a ship that looks like it's designed to fill a roll rather than just look pretty helps to bring a fictional universe to life I find
I find beauty in function but that's me.
Beauty is in the eye of the beholder.

