I've read Owen Barfield often enough to suspect that, when we speculate about the ancient poetic makers such as Homer, we are likely to beg certain questions. We assume that they and their world were pretty much like us and ours, except that we know a lot more than they do thanks to geographical exploration, the spread of literacy, the systematic use of the scientific method, and so on. We wonder how much of what they wrote, they wrote out of ignorance and erroneous ideas about the world, and how much was written, consciously, as fantasy, meaning by that the invention of material that they knew perfectly well as not true.
I suspect there's a lot of anachronism not just in our ideas about their ideas, but our assumptions about their minds.
In ordinary daily life, we experience the world as a series of objects that we look at and ourselves as, in the eyes of others, objects, and our consciousness as something centered in our heads and generated by brain activity. We touch our heads with a forefinger when we catch ourselves forgetting something, because we suppose consciousness is something going on in our skulls. We read articles in the popular press that hardly know whether there is a difference between "brain" and "mind."
People didn't always experience conscience-and-cosmos this way.
A way of getting at a difference between ourselves and the ancients (which could include people from even the Middle Ages, etc.), is to consider the word "genius." To us, "genius" is an aspect of a person. Einstein was a genius -- he was very smart, etc. But "genius" used to mean a kind of tutelary spirit that might descend upon a person, enabling him or her to do something extraordinary, and maybe even being a sort of possession of the person, but still distinct from that person. I'm not saying they were right and we're wrong or vice versa, but that they may have experienced poetic inspiration differently than we do (cf. Plato's dialogue Ion, etc.).
And nature or cosmos were experienced differently, too. For them "it" was pervaded with significance and a wise person sought to align himself or herself with the order of nature. For us, meaning or significance is something a person might or might bring to the experience of nature, cosmos, life, influenced by "society." The modern outlook -- the stuff taught in schools of education -- is that there's no inherent meaning in anything, just what's socially constructed. The ancients would have seen society, rather, as reflecting permanent and perennial reality (and as running into trouble when it doesn't thanks to human pride, ignorance, etc.).
I think an ancient poet probably felt that he or she was receiving images, words, etc. "from without," or that nature or cosmos or the gods were speaking through him or her. I don't mean to be taken to be saying the poet was in a trance or something. But there was more of a sense, I suppose, that something was being imparted, given. To be sure the poet's own skill came into play -- there was a lot of emphasis on the teaching of rhetoric. (For us, "rhetoric" even tends to have a bad connotation, e.g. "I'm sick of all that political rhetoric.")
So -- I'm not sure the ancient poet really thought in terms of the epic or saga as something invented or not invented, factual or fantastic. Were the great myths made consciously by individuals? I wouldn't bet on it. I suspect, rather, that they were experienced not as "explanations" of nature, but in a sense were given by nature ("nature" was different then) speaking in human souls.
I might be mistaken about a lot of this. For one thing, I don't know how close the things we call myths and read in books by Edith Hamilton, etc. are to what the ancients told and sang. Language itself was different. Barfield points out how, for us, the ancient Hebrew word ruach or the Greek pneuma have to be translated "breath" or "wind" or "spirit" by English translators, because we now experience these as distinct things. It wasn't necessarily always so. We separate as "literal" or "metaphorical" what may once have been a unity.
If that's so, then we may tend to misunderstand myth-making, poetry, fantasy, etc. the more the farther back in time we go.
But the study of words can help us recover something of the older consciousness. "Blood" might be a good one. They knew a lot less about the physical side of nature and so didn't have the medicines we do, but they were also, evidently, a lot less alienated than we are. What would be a characteristic physical artifact for our time? You think maybe a personal computer? But maybe a better choice to represent us would be a suicide note written by a physically healthy adolescent with a comfortable home, plenty to eat, little hard labor to do, and so on. Every year thousands of young persons enjoying these blessings can think of nothing more attractive to do than "ending it all." How very weird we are....
Barfield encourages us to read widely and deeply in literatures from before our time, and, as we do so, perhaps we will become more cautious about assumptions about the people who lived long ago, and even about ourselves.