In the beginning, we didn’t understand our world. So we created gods, spirits, and creatures like elves, dwarfs, and changelings to explain why people died from plagues while others thrived. Why a hunt could yield great rewards one day, and great tragedy the next.
Those myths gave the bards and poets something to work with, to entertain the troops and keep their bellies full.
I bet if we were to take a close look at all of the mythology we’re taught in schools, we would find that most of the stories we heard were originally the ramblings of a soldier drunk on mead as he sat around the campfire with his buddies, celebrating the spoils of pillage.
Of course, some people do worship the gods of old as faithfully as any church goer, but this isn’t about religion or spirituality as it is about these entities as characters in fiction.
No one has a copyright on the Greek gods, or the gods of any pantheons. It’s why we can have Hercules the Legendary Journey and Xena in the same decade as Disney’s Hercules. It’s why Sherrilyn Kenyon can include all of the pantheons of the world in her Dark-Hunter series and Neil Gaiman can write American Gods.
Run wild. Look at the old stories. See what perspectives you can add. Was Hercules really a legendary hero, or was he an overly entitled jerk who needed to learn to work for a living? What happened to the baby that Isis tried to make immortal, while she was biding her time to get the cornerstone of the house that contained her husband’s body?
However, there are people out there that will pick holes in your story. It’s true, you can have a character named Hades. But if he’s not the ruler of the Underworld, then your character is Hades in name only. And whatever you do, if you have a fully illustrated book involving a character that is a cucumber, do not name him Priapus, no matter how cool you think the name sounds.