A couple of things could be the issue:
1. Younger generations have been groomed to abandon religion
2. Churches have abandoned their First Love
What I have seen is also a factor. Churches have become dogmatic traditiinalists and unbiblical in the faith that they hold. Younger generations are not persuaded by traditions that they recognize as irrelevant. These include Arminianism, Calvinism, theories of the Atonement, and eschatologocal positions.
Younger generations not only want a faith but they want a faith that works. I've seen very active youth groups (College students) who reach out to the community, who fellowship in Chriat, who teach Scripture, who devoted themselves to God's Word, and who organize and ho on mission trips. They have a heart for God. BUT they don't have a heart for the theological systems men have developed and men use to identify their sects.