What is the quality problem with this image?

I doubt that the black & white aspect of the image is a problem here. And indeed it is a colour image, even that the colours are limited.

Even looking at the picture, I think that it is a very pleasant image, and it distinguishes itself from all those generative AI assets. But, if you have a more in-depth look, you see artefacts a little bit everywhere.

Example:

You see in the neck area a sharp line (arrows), where indeed a blurred line should be like the cloud. Or all the elements should be in focus, but then the sharp line is like over sharpened and exposes aliasing.

Artefacts (arrow) and noise (cloud):

And the image generator also “simulated” chromatic aberration, but chromatic aberration is a photographic defect.

The really bad part of the image is around the eyes, where the AI introduced many artefacts, that make the asset difficult to correct.