I left Christianity when I was about 16. I am 65 now. It is interesting to reflect on why so many people left the church. For me, my main issue has to do with the problem of popular Christianity--to be frank, it is just too shallow. I grew up with fundamentalist Christians. Their Christianity is a collection of fairy tales, and they tend to be literalists. For someone who is well-educated, especially one who knows quite a bit about world religions and the history of religion, this just would not do. I have studied the religions all my life and I have published extensively in Buddhism and Christianity. I find religion fascinating. But for someone who is in graduate school, how can one go back to kindergarten? Beyond this, there is also the imperialistic aspect of Constantine Christianity, which is quite the opposite of Prophetic Christianity. Personally, I think the teachings of Jesus are precious. But there is no future for a religion which insists that the believers stay with childish things. Christianity has a future only to the extent it becomes an adult religion and allows people to access its deep wisdom.