Sadly, some ex-Mormons say that many Mormons are so confused and made distrustful by Mormonism that when they leave it, they don’t go to a Christian church of any kind.
Unfortunately true, of much of Mrs. C_C's lapsed-Mormon family.
Fortunately, Mrs. C_C herself found conversion to Southern Presbyterianism to be quite spiritually vivifying, and liberating.
I would agree with that too. I don't know the statistics, but I'm fairly certain that a large portion of those people who leave Mormonism do become agnostics or even atheists. It's hard to trust any religion when you realize that you have been lied to and exploited in the name of God. Many of those who research LDS history and Doctrine end up feeling that way.