A more important factor when learning about myths is learning how to interpret them. There are a number of different schools/approaches here, and Campbell’s is one that runs into the problem of conflating similarities between cultures rather than paying attention to important cultural distinctions.

Unlike factual text or legal documents, which benefit from being inscribed, a story once written down — even one rich in analogy and metaphor that holds within it multiple levels of meaning — can, over time, become believed to be literally true, offer “right” or “wrong” answers, and stipulate ways of thinking or belief as well as modes of behavior,... See more