Fair enough (edit: wrote this, before the previous post was desceptively edited), but then let's talk about ehy you think my assumptions are wrong.

What good is changing your assumptions if the assumptions you are going to adopt are wrong?

I'm sorry to disappoint you but most of psychology and sociology have pretty clear answers to the questions you have pondered for so long. First of all you are wrong in assuming that truth is always simpler. The opposite is true: the closer the description is to the reality it describes, the more complex it becomes. This is also the reason for a few of the false assumptions you have: People are neither good nor evil nor are they irrational. Infact people are super predictable. 80 percent of our actions are steered by heuristics exactly because reality is too complex for us to grasp fast enough. This IS a form of rationality, but in complex scenarios it often leads to bad outcomes.

It is also why we are unable to construct a system that is impenetrable to corruption. Because corruption (as in a lack of balance, destabilising the system) is the very thing that keeps societies from dieing. A "perfect" system is a closed system, but a closed system cannot survive. It needs input, but every input introduces instability. There is absolutely no way around this.