Perhaps progress requires a move away from human-like brains. There are infinitely many kinds of potential intelligence. It's very unlikely ours is the pinnacle.
Then, gradient descent is a centralized and supervised learning algorithm that has nothing to do with all the decentralized and emergent processes that take place in biological brains. For example, consider all the complex interactions of the various neurotransmitters and neuroreceptors.
Biological brains (let alone human) are actual physical realizations of networks with very complex and specific topologies. New connections grow and are formed in a very real sense, and this process interacts with the environment in a variety of ways, plus it is spatially embedded.