More Words, Deeper Hole

Painting the cloak as a flat black shape makes the illustration look cheap, like the artist was too lazy or incompetent to do drapery.

It could be done. You’d either have to do the whole illo flat-style, very graphic-designy, or put a lot of stuff in front of it to break up the space and add visual interestor, or…. But you’d be designing the whole illustration around the cloak.