But that IS the definition of consciousness! This is like saying "We understand practically everything about airplanes, except how they stay in the air."

Nothing discussed in neuroscience is relevant to understanding what consciousness IS (which is the question posed above). Finding out that stimulating such and such a region makes us sad, or that this bundle of nerves activates before we're consciously aware of a decision doesn't tell us anything about consciousness itself. We've known for hundreds of years that there is a relationship between the brain and consciousness, finding out more details doesn't answer the question.

(Now, whether consciousness is necessary for AGI is a separate question.)