It fails because the environment contains too many stimuli, and each action has too many possible consequences. Unless the robot has been programmed to recognize which stimuli to concentrate on and how to assess them, it is hopeless at human tasks. Humans find them easy enough in practice, but the rocket scientists are baffled about how we manage them in theory. He concludes that the mind must possess a set of specialized, preprogrammed modules that are quite unlike one another, each designed for a task such as perception or social exchange. Evolutionary theorists reject the blank-paper theory for a related reason.
Many critics doubt it.
I am persuaded by Pinker's main claims, that our minds evolved by natural selection and that our mental abilities require elaborately designed programs. However, I have some fairly high-level disagreements. I could pick an argument with his theory of the emotions, with his idea that our mental adaptations are out of date in modern Western society, with his evidence from questionnaires, with his generally dismissive attitude toward cultural influence. Sexual jealousy, I agree, is a Darwinian adaptation that enabled some ancestral humans to outreproduce their more relaxed contemporaries, who did not end up among our ancestors. But to show something is an adaptation says nothing about how easy it may be to modify.