Because I'm a highly critical curmudgeon that demands things be made to a high standard.
I'm not actually hating anyone, I just would have, as an editor, product owner, or art director sent that back as unacceptable poorly thought out work. I don't mean to seem hateful about it, but criticism is a part of the refining process. You put out your stuff. It gets kicked around. You get angry. Then you sit down and you try again until you get something that has passed through the fire so many times it's pure gold or at least brass-plated and bulletproof.
However, if you want to defend the artistry, feel free to stand up for what you believe in. I might argue with you. I might think you are full of crap. I might end up thinking you have no taste. But I'm not going to respect you less for disagreeing, and I'm certainly not going to hate you for it.
Let me put it too you this way. Suppose you wrote a fantasy novel, and knowing as you do that people will judge a book by its cover, would you want that image to in any way represent your book? Suppose you were writing for an audience that you know spanned everything from 12 year olds, to 60 year old HEMA experts. Would you want your work represented to that audience by that? Hitherto, a lot of the 5e aesthetic harkened back to the better elements of 2e art - which I consider the high point for D&D (though I like the old school ink drawings as well). This however looks like it escaped from the worst of the 3e/4e era: all the sloppiness of 3e art, combined with all the unreality of 4e art. And that's not even to get into the fact that the art is representing something in the fictional world that is just plain silly.
