Just a point about your hypothetical. It does nothing to distinguish between
genuine foolishness and spiritual truths. I think that we would both agree that the Flat Earther's are simply foolish, not "spiritual"
In fact I would say that it is hard to judge ideas about the history and operation of the physical universe as "spiritual truths" - indeed they would seem to be natural truths by definition.
And is a literal reading of the Bible really the best way to extract spiritual truths ? Wouldn't a preference for literalism be more likely a mark of a "natural mind".
Now if you want to look for spiritual truths perceived as foolish be the world, how about loving your enemies ? Giving all you have to the poor? Choosing to live in poverty, trusting God to provide ?