No one has ever claimed AI cannot imitate a Monet, but however good the imitation, it still isn't art any more than a Xerox of a painting is art. This is the exact reason why most people feel bad after discovering that what they felt was work of human ingenuity, is just a fake, a simulacrum of it. The creation of art, arguably the most human of instincts, cannot be separated from the emotions and effort that went into it.
All this proves is that most people cannot tell if that picture is a Monet or not.