Trying to figure out what kind of art AI art generators generate is a category mistake. They don't generate any kind of art if one uses the standard definition for art.
MW's definition is adequate: Aesthetic objects produced by the conscious use of skill and creative imagination. (Definition 4, rephrased for brevity.)
It is somewhat weak, because aesthetic object is underdefined. Objects or processes produced by the conscious use of skill and creative imagination for the purpose of evoking aesthetic experiences would be identical but more clear.
AIs do not have consciousness, skills, creativity, imagination, or intent. Therefore AI art generators do not generate art, they generate things that look like art. This is not a new phenomenon. Natural environments look like naturalistic art. People look like portraits. The Smile Nebula looks like a crude smiley face. Nebulae make an especially good example because most of them don't look like anything until you input the right inputs into an expensive, complicated machine (a space telescope and its image-enhancing, color-magnifying software).
Nor do humans using AI art generators generate art in the first instance: they discover things that look like art in their environment. They do create art if they do anything skillful, creative, and aesthetically intended to the generated picture (like cropping it and putting it in a frame), exactly as one can create art by drilling a hole in a pretty shell and putting a string through it to wear it as a necklace.
Imagine that we lived in a time and place far from the sea with no trade to the sea, where experience has taught us that pretty baubles that you drill a hole through and wear as a necklace must always be crafted by human artistry. Then making your shell necklace is still art, but telling people that you made your shell necklace yourself, without explaining that the shell is just something you searched for on a beach, is a lie.
Since AI art generators are labeled as they are and advertised as a way for the user to be an artist, I suspect that in the very near future, the definition of art will have changed to include "or machine-generated objects or processes evocative of the above". I predict that we will soon have a new word denoting art of conscious origin to distinguish it from new-definition "art" in general - almost all of which will be generated by machines. (As with music vs live music, in which the original stuff gets the compound word, while the recorded stuff swiftly usurped the original word because it's much more common.)