Freud’s naive assertion: The impossibility of neurological correlate of Freudian psychological model

I remember when I was first expose to then fantasized by Freud conceptual model of human mind, the obsession is no less than jumping in love with someone. But as the passion recede I begin to see theoretical issues in his framework, what really repel me is his tendency to mechanization of human mind by suggest that maybe we should look for neurological correlate of Id, Ego and Superego. How on earth is he thinking?
For me, psychological world is an abstract representation of the biological functioning of brain in coordination with other organ. I admire his heroic effort to put the human body and biology back to where it suppose be, but psychology is different from biology. They must be distinct disciple of empirical research
. As anyone could imagine: the operation of something must be somewhat different from the structure of something, granted the assumption that psychology is nothing but operation of brain. What Freud is studying is how the psychology in operation, it would difficult in logic to reverse engine what biological structure lies behind the operation of psychology. There are really many ways to abstracting the mind, Freudian framework is just one out of many. How on Earth must he think that is the only valid way(so the correspondence with neurological structure implies)?
What happen if we push this idea to its limit: Id, Ego and Superego are three functionally distinct neurological structures. That means there are some brain damages/disease/condition which would weaken one but not another; that would be an interesting observation if it corresponding to observation by medical doctors Since Id, Ego and Superego are built in process of socialization, it follows that socialization process would alter the structure and functioning of human brain; so do psychoanalysis. Beside, since our psychological process is almost a reflection of biological process of the brain, that would be really amazing that human civilization could advance as much as we seen today!
The core difference between me and Freud is: I see thinking/emotion more as a process that represent advance usage of neurological structure, which is why human could be seen as a step forward in evolution that layers of flexibility is what give human freedom its essence. In Freud’s mind, human is mechanical and deterministic, which is yet to be demonstrate.