I don't want to speak too much out of my depth here, I'm still learning how these things work on a mechanical level, but my understanding of how these things "reason" is it seems like they're more or less having a conversation with themselves. IE, burning a lot of tokens in the hopes that the follow up questions and answers it generates leads to a better continuation of the conversation overall. But just like talking to a human, you're likely to come up with better ideas when you're talking to someone else, not just yourself, so the human in the loop seems pretty important to get the AI to remix things into something genuinely new and useful.