our understanding of the brain is so basic

This feels disingenuous at best, and woefully uneducated at worst.

What are you even talking about? We have entire degrees (at all levels) focused on the brain and it's limitations, procedures and inner workings - and that's on top of the hundreds of years of data from psychology, both understanding the internal representations of the mind and learning.

We know a shit load about ourselves. Philosophically, we struggle to understand consciousness and the basis of it; but as a science the brain is well understood, lol.

A more interesting point than "we don't even understand our own brain" is that AI functions as a reflection of what we know about humanity; I've always figured that eventually we will define a different model of intelligence that reflects what we want AI to do. For example, have humans really evolved the most advantageous way for communicating now? Maybe there is a better way to communicate, and we can code and engineer that intelligence without mimicking a human.