We never hear about him again, but I think the character of Nicodemus is meant to be a stand-in for a lot of us who are not quite there yet, but are on the way. He certainly stands in for Christians who seem to be stuck in Stage Two, thinking too literally about the stories of our faith. Whether we regard them as historically and factually true or dismiss them as nonsense—either way, we miss what the Spirit is trying to do: bring us to a deeper, richer, more multi-layered and contextual understanding of these stories and to a more God-filled experience of their truth for our lives today.
If it's any consolation, young people just starting out are not the only ones who feel that way. We can get stuck in the birth canal at any time of our life. In fact, it's much worse the older you get. Then it's not so much that we're stuck waiting for life to begin. It's that we get stuck not believing that our life can change. We're stuck with a body we don't like, in a marriage that doesn't work, with a job we can't stand, a mortgage we can't pay, or a disease we can't cure. When we graduated from high school, the world was full of boundless opportunity. Now that we're much older, we start to see a world of endless impossibilities. Welcome to the world of Nicodemus.
To be sure, the early Christians argued over who Jesus was. That's why the Creeds were written. But they never settled the question of exactly what Jesus did and how he did it. We are accustomed to saying that Jesus died on the cross for our sins, but it isn't immediately obvious what that has to do with our salvation. There is no clear, logical connection between his death and our life. So the cross needs some interpretation.