What does derivative mean in this context? That he’s copied a photo?
Derivative of earlier art movements. Notably Warhol’s pop art.
Warhol’s artistry wasn’t in technique, or really even in composition. It was in the ideas. And ideas are personal, individual, they communicate to the audience.
Warhol took the commonplace (like the soup can or detergent boxes), and said “what if these cheap, ordinary bits of design that epitomise American life were rarified, made iconic?” Which is kind of different for us where we stand because later brand identities have done that.
Or he took the celebrity imagery that said “these people are rarified and special” but whose images were mass produced and disposable in magazines etc, and he distorted those photos, their colours, or overlaying them etc. - making them expensive and unusual but also challenging their perfection.
And then the mass production of his imagery adds another layer of these contradictions.
And Warhol wasn’t alone - Lichtenstein did it with comic books and so on… and they’re art because those ideas are new and intriguing and they speak about that time and place and the artists.
But if you create art which very directly uses the same ideas as another artist, and many of the same techniques and compositions, it’s derivative. It’s not art.