Hi there! I am a player of TTRPGs since 2004. I have found dozens of similar games from fanmade to official ones. I have even got my player on a fully improvised adventure with all fresh ideas I had never used before, until one of my players ask me if I was taking inspiration in a manga I didn't knew it existed that was clearly a mirror of the adventure. You can't creat something new. But you can create a new gaze upon something. Look D&D, dungeon world, pathfinder, starfinder and so many more take a pot of it and made a new version. Don't beat yourself because there are a lot of games with a lot of different settings, rules and characters that are similar to other already made. And if you made your own Shadow run, my recommendation(from someone who tried several times to do what you are doing), compare them. You can see where you got different rules and solutions, where you took the same answer as the developers and where you choose different. I mean look it to learn from it. And if you think you can't use it, think or 5he Divine Comedy, it's a fanfiction of the bible with a self insert from the author in wich he meets his favorite writer and team up to rescue the woman he loves. If Dante could pubish that, you can make something with yours.

TL,DR: complete originally don't exist. And that is not bad. Dust yourself and keep creating. Sorry for the bad English. It's not my first lenguaje.