I've been wondering why this argument's not been sitting with me, and I think it's for the same reason that the courts have ruled that the FBI needed a warrant to put a tracker on someone's car, as opposed to following someone - the scale of action enabled is the differentiator.

A student learning from other artists is still limited in their output to human-scale - they must physically create the new thing. An AI model is not - the difference between a student learning from an artist and an AI model doing so is the AI model can flood the market with knockoffs at a magnitude the student cannot meet. Similarly, the AI model can simultaneously learn from and mimic the entirety of the art community, where the student has to focus and take time.

If this weren't capitalism - if artists weren't literally reliant on their art to eat, and if the market captured by the AI model didn't inevitably consolidate wealth - then we might be able to ignore that, but we do, and we can't ignore the economic effects when we consider scale like this.