You almost hit the nail on the head. Disney is not to blame in this situation at all. One of their designers went to shutterstock (totally normal) to buy and use some art (again, normal, industry standard), shutterstock sold the art that had been uploaded by an independent artist (that’s how this all works).

HOWEVER, the artist used AI to create his image and neglected to add the “Created using AI” tag to his art which is required by the terms and conditions of shutterstock.

In this instance both Shutterstock and Disney got taken for a ride and are getting the negative press because of an individuals decision.

You could technically blame shutterstock a little bit for not vetting what they host but as far as I am aware there are no reliable tools for determining if an image is AI with 100% certainty.