From your description, there was no good being offered. So people who are corrupted generally don't understand the difference between good and evil. Although there could be exceptions.The point overlooked is that Adam and Eve chose to have knowledge of both good and evil. People therefore knew what was good and what was evil.
The Adam and Eve story is not to be read as being literally true, but that doesn't mean that there is no lesson to be learned from it. I'm not hearing the message, other than you suggesting that A and E chose knowing of good and evil. Maybe more to the point is that the message is that they chose to act out evil.
I've never heard of any description of the evil they chose, save eating fruit that was forbidden.They were choosing evil/corruption. They could have reformed any time they chose to do so. Keep in mind that Noah was referred to as righteous, so at least he was seen/known as choosing good over evil.
There's a message to the story but it's comparatively weak considering the details of the story.
Maybe I'm missing the more important message?
It appears that you're really not interested in leaving out references to the stories in the bibles that are now accepted as allegory, and not literally true.