Think of it as this way:

in order to create 5 very different illustrations you need to talk with 5 people. in the end 5 people will get money when they finish with their work.

an AI consumes these artists past output and instead of paying to these artists it will gather income to the owner. So by using the output of 5 people who have spent decades on perfecting their craft, the AI generates income by stealing their work, and the money flows to the owner only, who doesn't give back anything to these people.

so in essence AI in this form kills income stream for humans, since it gives back nothing.