The topic of myth-writing came up on the pagan board where I hang out, and I was asked if I believe that modern myth-writing can be "true" and "valid" and if it even counts as myth.
My one and only criteria for anything spiritual or magical (or psychological, for that matter) is "does it work for me". If they work for me, I trust them and they are valid for me. What "validity" established myth has is an illusion half the time anyway. (Ask a group of academically-minded Asatru about Snorri sometime. It's fun.)
I don't necessarily believe that stories have to be relevant to anyone besides me to be worthwhile, just as you don't necessarily expect your journeywork experiences to be relevant to other people. Sure, they might be fun or useful to share, but that's not their primary value.
Writing can be very much like journeywork, actually. It's very easy for me as an author to slip "into character" and experience the emotional arc of a story along with my protagonist. I write fiction, particularly mythic fiction, with an eye toward figuring out the story. I don't know how it's going to end when I start.
It's not unlike automatic writing, in that I intentionally seek a state where I'm not in charge of the writing process. The poet Jack Spicer called it "taking dictation" and I particularly like that turn of phrase. I certainly do feel like I'm taking dictation when I write.
Some people will attack paganism, claiming that the ancient myths are just fiction. I think that's a plus, personally. I want a religion I can write, that I can play a role in shaping.
You want tangible, social benefits to writing fiction? There are people walking around today because other people wrote words that spoke to them. That’ll do. -Warren Ellis