Human intelligence is bootstrapped by biological evolution and the society, neither of which is fast or efficient. Truly individual part of the intelligence is tiny, it's vastly overrated and relies on these two. Similarly, LLMs perform in-context learning, which is much more efficient because it relies on the pre-baked knowledge. Yes, the generalization ability is still incomparable to humans, but it's entirely possible that much better ability is achievable by slowly bootstrapping it.