for me what separates art from AI is intent or deliberation. Amazing artists tend to be extremely deliberate about what they are doing. Nothing is left to chance, or if chance is involved, that is also again a deliberate choice (e.g. in alleatoric composition).
Slop doesn't carry intent - stuff is just there because LLM put it there. Art is full of deliberate decisions in every detail. In slop you better squint a bit to not notice the details.
Same argument can be made for code. AI code is always "coding by coincidence". There is code and it kinda works. In good code, every piece is intentional and needed.