It's possible to take an existing idea and give it a unique spin. A lot of games today are just recycling old concepts but in new ways, so don't let it dissuade you. You'd be surprised; there's still jam games from years ago that I come back to today. One of the neat things about being able to build games is you can build the ones you want to play. There's no prizes, so don't think too much about what people might want - just build something you want to play (while avoiding copyright infringement obviously).