Fantasy is just another word for Alternate Physics.
Do you enjoy power gaming TTRPGs? No? Maybe this ain't for you.
Otherwise, steal someone else's idea and make it your own.
Look, Fantasy is just the backdrop. Take any other story you wrote and swap out phones for Talkie stones, Fire bolts for bullets, and Elves for the Swedish Bikini Team.
add in a healthy amount of rocket tag and then used that as the BACKDROP for whatever your story is about.
Look. Read HKN. It is a Fantasy. However, none of the plot lines have much to do with the fantasy. It's about racism. Intolerance. Being born a hero vrs being evil and having to fight to overcome your nature. Its about loss, and fathers and sons having terrible relationships and the mistakes made when people don't communicate.
Yes, there is magic and a demon lord and a western European ambient setting, but that's just the backdrop. I could have changed the magic into psionics, the demon lord into UltraTyrant, and set it in dystopian nuclear hellscape and out fit the MC with cybernetics instead of magical tattoos carved into his flesh.
The story would be the same.
Fantasy is just the Skin you put over the framework of a story, not a story itself.