I think "rough" is understating it. Galileo finding different sized objects fall at the same rate, knew more about gravity than we know about intelligence. By analogy, in terms of gravity, our understanding is at the "Things fall downwards" stage. The Newton's Laws of Motion for intelligence are a long ways off yet.
If you look at the human brain as a computation device and the mind as the software, evolution as the design process, you see that biology has been iterating on the very problem we're trying to solve for hundreds of millions of years, billions if you include abiogenesis.
We don't really understand how the human brain works. We don't know how nature engineered our own initiative. We have a rough idea of the algorithms involved, but understanding those algorithms in detail is not going to be easy.
It's always going to be much much easier to fix the human brain's limitations than it will be to re-engineer a new one. So the economic case for strong AI isn't ever going to really exist, because first we have to build the world where human-level AI is a thing.