This is not a problem because there is no such thing as generalized AI. There's just specialized AI for lots of things added together. Keep getting better at things and after a while you are good at lots of things, so appear to be general to an observer (until they see you outside your domain of expertise).
This theory compactly explains why no one knows how to do general AI.
I don't believe there is a special sauce waiting to be discovered.
That's not what General AI is though (at least how I define it), real AI would have to be able to invent new things, not just be good at existing things.
Many humans go their whole lives without doing that, so I'm aware it's a high bar. But it's a bar that some humans do pass, and if AI is to be more than just a helpful gimmick, it'll have to do that as well, since I'd like to believe all humans have that potential, even if not always realized.
(Obviously a helpful gimmick still does have value.)
But brain still is "just" a neural network, granted, with immensely more complex neurons and extraneuronal mechanisms that might as well be absolutely crucial for learning. But the difference between a highly intelligent and blank-stare person can be as small as switching off a small part of the brain or tweaking a neurotransmitter. Which shows me that general intelligence is something extremely sensitive as oposed to something like vision processing, which takes much more drastic changes to disturb.
Looking at the brain, it often does look like a bunch of interconnected specializes neural networks.
This theory compactly explains why no one knows how to do general AI.
I don't believe there is a special sauce waiting to be discovered.