I think that story is intended to show us that perfect faith is not expected of us, nor is it desirable for us.

Abraham's life was such that he developed it. That is admirable in a sense, but it's not for us. We are expected to evaluate things for ourselves.

This makes "what would you do if God told you to kill your son" entirely inconceivable to us, because we simply do not have that relationship. We're not supposed to be capable of answering yes, because we're not close enough to God to have that override everything we understand about morality.

And we're not supposed to be, and getting into a mental state in which you can imagine killing your son would be monstrosity, not piety. Even Abraham had to argue with God and see that Sodom and Gomorrah really did need to be destroyed before he was capable of that kind of relationship. For us to override ourselves in that way without that kind of experience is a presumption and an abomination.

It is for Abraham. Not for us. Without all the other things that go along with it, it is not right.