You believe the best decision is one which can be easily changed meaning

This is not true. I strongly disagree with this statement that people believed that the best decision is one which can be easily changed. The good decision is the one that is never can be changed since it means you have thought of it deeply and sincerely before people made that decision so there would be no reason to change it. A decision that is made to be changed means not a good decision since you need to modify it because you are unhappy with it and unsatisfied.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.