You are aware that scientists still can't fully explain the most common mental process that takes up 30% of our lifetime? The human brain will never be perfect

You are aware that scientists still can't fully explain the most common mental process that takes up 30% of our lifetime? The human brain will never be perfectly replicated in this lifetime or any lifetime, in the same way that a group of toddlers would never 100% figure out the full technology and complete mechanical blueprints if they were handed a Ferrari. I don't think that's clear at all. I might agree with your first point, that we don't understand the internal mechanisms very well, but in some cases it's a lot easier to model a system than to understand how it functions. This is particularly true of emergent behavior, which pretty much anyone in the field acknowledges the brain is largely driven by. Even in fields as concrete as physics, there are plenty of emergent results which can be verified to arise from the small-scale behaviors that we can observe, whereas a full "understanding" of how that emergence happens is beyond our grasp.