I found this article to be hopeful and realistic about youth ministry in the context of Post-Christiandom.
“...as we embrace doing ministry in our current culture we must remember that Jesus did not call us to efficient programs or growth models. Jesus calls us to himself and then sends us to people. There is no greater work than being sent by Jesus to a people who do not know him, being faithfully present with them, and inviting to share in the story God is working into our lives. This is the way of Jesus and it is the way of youth ministry in our post-Christian world.”