I'm not sure I follow what your argument is here? Just for your information, Robert Sapolsky is a neuroendocrinologist from Stanford who has been studying this exact subject for the past 4 decades. The book agrees with your point that looking for a single reason to explain human behavior is impossible and a lot of things contribute (hence why he covers so many determinants of behavior, such as what is going on in your brain, your genes, what is going on with your hormones, where you were born, how you were raised, etc).

I don't see why the nature vs nurture debate is stupid or why how old it is matters? Clearly both things determine human behavior. The main point to be made in Sapolskys book is that almost all determinants of your behavior are out of your control. You don't choose which country you're born in, what genes you have, whether your brain develops properly, whether your parents are kind people or terrible people, what neighborhood you grow up in, what race or gender you are. Perhaps you should read Sapolskys book.