I think hermeneutic analysis acknowledges a difference between “myth” and “fiction.” Calling myth fiction is a simplificatio,n appealing to the “common man” atheist. However, a myth is acknowledged as a story with a high probability, even if as described in its particulars, it didn’t necessarily happen exactly that way.
When I write about the Abraham “myth“, as I have several times in journals, I am talking about “archetypes” or patterns of behavior characteristic of “humans-as-species” in the jargon of evolutionary psychology. For example, God’s leadership of Abraham is consistent with what we still teach as “situational leadership“. For modern people to believe in the rightness of a leadership style that ancient Sumerians and Hebrews also saw as right, suggests a continuity over 5,000 years. That is suggestive of genetics, since the belief crosses so many cultures over so long a time – literally, all of recorded human history.
As for Mormons, I have no opinion. As for scientists, a single study needs confirmation. If, as Kelly Crowe of the CBC reported, up to 50% of scientific studies are fraudulent, believing this one about the Book of Mormon could be a coin toss. And even if regarded as “true”, what does that mean? Science deals in probabilities, not absolute truth, which is impossible to establish in any event.