Other factors accounting for the exodus are the strict disciplines that have often harsh requirements in order for the congregation to participate, like the Catholic faith, but then there is the latest barrier, an LGBTQ community that isn't welcome, especially by Evangelicals. Here are passages from the Bible re. homosexuality...
You shall not lie with a male as with a woman; it is an abomination. (Leviticus 18:22)
If a man lies with a male as with a woman, both of them have committed an abomination; they shall surely be put to death; their blood is upon them. (Leviticus 20:13)
According to one source "The word “homosexuality” didn’t even show up in English translations of the Bible until 1946," so Bible thumpers can't really trace it back to the original scriptures. And that brings about another theory of mine, the Bible is a book written by men who, even if inspired by the holy events of the day, nevertheless were people like us. Prone to mistakes, which in many cases account for confusions found in translation after translation. But the obstacles against the LGBTQ group is only one problem for the church; with so many more, the "nones" are sure to proliferate.