Myth and story is a language.
We do not say a new sentence by creating a new language.
But if you will go and learn the old language of man, you will bring forth treasures so old and so true that they will ring in the hearts of readers, if only because they rang in the hearts of their fathers and mothers for thousands of years.
The world itself has themes—ancient themes—and to write in those themes is to weave something into the fabric of history.
Originality would have you devise new synthetic threads to create a sweater which expresses your own individuality. If that is your desire, you may do it—but few will wear one sweater. (Though a sweater made naturally is a very pleasant thing, no lie)
The world’s best stories, whatever the setting, weave easily into the story humanity has always told and lived—and the one who sets out to tell them will often find the threads they were using were already attached in the first place.
It feels like discovery. It feels like finding something which was always meant to exist. It tastes like fruit off the vine of humanity, and something one man or woman could never do.
For the vine is tended by Someone else—and the tapestry does not display the originality of one mere man, but the King after whom the pattern of mankind and and all their truest Myths is fashioned.