I'm sort of thinking that Arthuriana is occupying more the place of folk-tale than religion. It's there as a source of tropes more than it is as a source of moral guidance, which I reckon is what religion directly provides. So, it's less rigid than religion? Though I dunno, maybe it also depends on how pervasive it is, because religion is pretty pervasive and there are so many profics about religion too e.g. Behold the Man, According to Mary, The Red Tent.

These stories and folk tales and folk wisdom are totally still with us, so they totally affect us. But how? How does folk tales affect us as opposed to religion?