A lot of people worldbuild when they daydream and have the bones of a story kicking around in their brain, but have to pay the bills and raise the kids etc so they never flesh it out and write it down. What’s your story’s premise? Fantasy, sci-fi, alternate history, mystery, western, whatever genre.
I’d write a sci-fi story, which explains the fermi paradox. There are thousands of alien races all over the galaxy, but they basically all took one look at humankind and said “fucking hell no, those guys are absolute dicks”.
I’ve got a similar story that I’ve been workshopping for years…the alien races decide humans are too warlike, and after our first space war (against other humans, with us not knowing aliens exist yet) the alien council ruling the galaxy decides we’re too dangerous and getting too technologically advanced, so they send an AI to try to wipe us out. Galactic civilization has been largely peaceful for tens of thousands of years so they don’t know how to do war, but they program an ai to try to eliminate humanity while preserving the rest of life on Earth.
They mostly succeed, but in the conflict the earth does get devastated despite the best efforts of the AI. A human colony ship escapes, and hundreds of years later the descendants of the massacre return to wreak bloody vengeance on the rest of the galaxy.