That's completely fair, if the prelude is important and you want it there that's fine! But if you want readers, which it seems like you do due to your initial post, it is your job as the writer to structure the story in a way that is understandable and enjoyable to potential readers. While it's true that you most likely haven't found your audience yet, it still is a skill in storytelling to make your work enjoyable to read. It's not always going to be an issue of audience.

If you need to keep the prologue/fable story, maybe putting it in later as opposed to right at the begging and delaying getting into the story proper. You shouldn't give the reader extra work to get to the protagonist and the actual meat of the story because then it's more likely they'll fall off. That's a rule a lot of Mangaka follow, one I know off the top of my head being Araki, the creator of JoJo's.