It is true, we will never know in the ultimate detail how each weight of each neuron must be placed and why. But that is simply because it is too intricate to u

It is true, we will never know in the ultimate detail how each weight of each neuron must be placed and why. But that is simply because it is too intricate to understand everything. Just like we try to understand human behaviour not by understanding individual neurons, we reason on an abstract level, called psychology. To take your example building a SDC will teach us which aspects are the most complex, and which solutions work better than other for those aspects. Comparing those solutions will allow us to see what working solutions have in common, and give us theories that we can then test.