Fiction is the only form of writing where you don't know what you're writing. How truthful is it? How duplicitous? How good/bad or (a)(im)moral? How will it strike the reader, especially (or even?) fiction with didactic propensities? Where does it come from? Its aesthetics that burn through your own disintentionality?
Characters you supposedly create sometimes take over and make the piece even more unknowable as to direction and purpose etc. This is what defines fiction. Not knowing what it is.
Or fiction is knowing about everything that is not known.
"Both wanted to sit down in the shade at the edge of the woods: neither would suggest it."
from A Game Of Hide and Seek (1951) by Elizabeth Taylor
i.e. hiding and seeking truths amid the unsynchronised omnisciences of more than one fictional mind.
Chasing a noumenon.
Fiction is like two unknown but gradually known characters or threads that eventually may blend (almost beyond the writer's control) across some vast waste (in one case between the unknown and the known, the other between two beautiful minds whose two bodies happen to be in a Freak Show Circus trailer - as metaphors for the divide between writer and reader) by means of imputed incarnation-by-fictipathy or simply by imagination...
'Fictipathy' (a word I invented) has indeed become mainly concerned with the pathology of fiction, but also, more recently by common usage, it has become to indicate a form of active telepathy by fiction - distinct, however, from the more passive Jungian 'Collective Unconscious' or, even, from what I would call 'nemoguity'.
On the other hand, fiction is probably more akin to a transcending of genre, reality and self - not through what I described as 'fictipathy' above, but as a designer of words into non-pragmatic patterns. Stories are indeed unpragmatic (ie of no possible use) but they do allow one to evolve abstract musical journeys with extrapolated (pseudo and real) memory- or dream-recall resonated by the ricochet -- a ricochet of meaning, look, sound and syntax -- which the words inexplicably form plotically (as well as poetically) within the reading mind.
This may be relevant to other discussions about what is wrong with certain fiction genres. It is the genre that is wrong, not the stories that make up the fabricated genre. It is the self that is wrong (both writer and reader), not the 'ricochet' described above.
There is much fiction *about* religion but very little fiction that aspires to *be* religion.
And for 'religion', please read 'empowered spirituality' rather than any single sect of religion. Or it is, as I have said before here, magic. Magic in itself rather than about magic.
I think the Horror and/or Fantasy genres (not sects!) are the most likely to achieve this goal. And those who have approached it (even if it was not their conscious goal): Lord Dunsany, William Hope Hodgson, Robert W Chambers (King in Yellow), HP Lovecraft, Arthur Machen, Elizabeth Bowen, Thomas Ligotti, Rhys Hughes, Jeff VanderMeer, Susanna Clarke...
Or is this a cul de sac, because you feel that 'religion' cannot be attained by fiction. Nor should it try?