Living in a society with limited understanding, what does the narrator yearn for and value in "By the Waters of Babylon"?

John longed for knowledge beyond his community.

John’s community is aware that there was once another, more civilized society before the apocalyptic event.  Those people have become gods, and anyone who interacts with their artifacts is a priest.  Since John is training to be a priest, he knows more than most of his people.

We are not ignorant like the Forest People... We do not eat grubs from the trees, we have not forgotten the old writings, although they are hard to understand. Nevertheless, my knowledge and my lack of knowledge burned in me—I wished to know more. 

John goes on a spiritual journey to find out more about the gods.  His journey is to the land of the gods, called the Dead Places, and he goes alone.  He is frightened, but curious. 

Once John gets there, a place called newyork, he looks around in awe.  He thinks that he is looking at the place the gods once lived, but as he gets closer, he realizes that they were not gods at all.  They were just people who built a great city, but were destroyed.  This knowledge makes him come to a new realization.

We shall look for the images of the gods and find the god ASHING and the others—the gods Lincoln and Biltmore and Moses. But they were men who built the city, not gods or demons. They were men. I remember the dead man's face. They were men who were here before us. We must build again.

John is now ready to lead his people to the truth.  He is proud of the fact that his people are not primitive like the Forest People.   His newfound information makes him wise.  He is convinced that his people can rebuild their society and be every bit as great as the people they once called gods.