My reaction would still be, "This is a pretty bad children's book." The reason I might not have guessed it was a machine creation is that the prose is adequate

My reaction would still be, "This is a pretty bad children's book." The reason I might not have guessed it was a machine creation is that the prose is adequate on a technical level, and previous markers for machine creation included wonky prose. But going forward we'll all learn new markers for machine-created dreck.