Instead of believing that their fallible human theology is infallible, they need to realize that if their theology teaches them something that clearly is not true (eg, earth no older than 10,000 years), then it is not God that is wrong, but rather their own theology and that that theology needs to be corrected. I view their inflexible refusal to admit that their theology could be wrong is a major cause of deconversion.
Upon reexamining this topic, I note that it asks good questions.
What can I (we) learn from talking with people who once believed as I do yet moved on? Ultimately, by examining the faith (or lack of) among others, we can learn more about ourselves.
When I use a word, Humpty Dumpty said, in a rather scornful tone, it means just what I choose it to meannothing more nor less.