I think that myths--and really all stories that are worth telling--circumscribe something that can't be told directly. It can only be told in drawing the connections, working the metaphors, writing the characters' changes, taking the heroes through fire. When a story recapitulates something universal in a new way, it becomes something powerful, nearer to myth. I also think that in reading mythical narratives (including those novels and memoirs and other accounts that build on a mythological archetype) you should always be aware that the interpretation will change, that others will interpret differently, and that each interpretation shows a different true facet of the myth.
Take something like slaying of the Minotaur, slaying of the dragon. What secrets enable the slayer to prevail? What does the dragon or Minotaur represent? Why does it have to be slain? Why is this hero successful? The answers will always be different, depending on who you are and what stage of life you're at. You can go back to those archetypes, like Icarus, and Sisyphus, and Leda over and over and still pull something different and retell it in a way that still works. For that reason, it's very important that they are not seen as morality tales.
About that show, I watched that a while ago and I was annoyed by Moyers always inserting the god concept in, when Campbell is careful to avoid it. (Though I do agree that Moyers can interview well, when he quits trying to lay an agenda on someone.) Campbell talks about his ideas about the sacred, the creative, and the individual in a way that allows for many levels of understanding, where Moyers kept trying to put those ideas in the box labelled Christianity.
Campbell also understands that the trajectory of myth and heroic stories is about the human desire for transcendence--something that everyone desires but few find, which is where the stories' power lies-- and that finding that experience is possible if you don't get swallowed up by the dragon that is all around.