There are some parts of the brain we have no clue about. Episodic memory or our higher level ability to reason. But most of the brain is just low level pattern

There are some parts of the brain we have no clue about. Episodic memory or our higher level ability to reason. But most of the brain is just low level pattern matching just like what NNs do. The constraints you mention aren't deal breakers. We can make RNNs without maintaining a global state and fully unrolling the loop. See synthetic gradients for instance. NNs can do unsupervised learning as well, through things like autoencoders.