There are two types of art. Art that emerges from creativity versus art that’s intended to sell.
The first type is generally arbitrary. How it’s graded though depends on its freshness. If we’ve seen art like it before we’ll probably not be that intrigued.
The second type of art is designed commercially. It most likely contains a figure that alludes a specific message about a product. When we see this art, we don’t even call it art; we call it marketing.
Whatever type of art it is, it ultimately gets judged by familiarity and experience. True art is something instinctual; an assessment made after years of studying and seeing other works. One can tell immediately if a piece stands out.
Commercial art, on the other hand, always needs tweaking; it means different things to different people. Grading is not done via gut check but rather a consensus.
Real art can’t be justified; you either “get it” or you don’t. The immediate understanding takes years of experience. An explanation as to why it works is not required.