I can't speak for all fantasies, but most of the ones I've read lately take place in universes where the why and how of their beginning (whether naturally evolved, created by a god or gods, or something in between) isn't really a part of the story or definitively known by the characters within it. For most of the history of our planet people had no idea how the world or themselves came to be, but they still had adventures and wars and epics etc. Of course, people had ideas about how things were that were far from accurate. I do try to work the beliefs and understanding of my characters into the story. Whether or not they are always correct? That doesn't generally matter.
If I were the write a story where the gods are the literal and real creators of your my universe, and if they are acting in the story in an unambiguous and salient way as the story unfolds, I can show this when it becomes relevant. Or I can keep the nature (or even existence) of the gods more vague or ambiguous. My characters tend to be ordinary people trapped in extraordinary circumstances. Even if they are magically talented, they are human first and foremost, so I try to reveal their nature and abilities as the tale unfolds.
As for the backstory of the particular protagonist(s), regardless of their abilities, I tend to focus on revealing what a given viewpoint character would be aware of and thinking about as a scene unfolds. Relevant backstory can come out as the characters act and as they react to the things and events around them, as can the relevant history of the world and the details of how magic works in that world or whatever. I prefer writing in a more character-driven narrative viewpoint (such as first or a somewhat deep limited third), but even if one is writing in omniscient, trying to toss too much backstory out there via long info dumps can be awkward. Even classic fantasy writers like Tolkien confined much of their info dumping to appendices and/or relatively short prologues/intros, and to relatively brief nuggets if information as the story progressed.
Note, I am not a published fantasy writer, and my attempts to become so have not been successful thus far. The views expressed here are my own, based on my own taste.
Check out fantasies by some of your favorite authors, and be sure to include some recent novels as well in your reading. How do these authors provide needed backstory and world building details without bogging the story down and tossing more at the reader than they need to know as the story unfolds.