What new library could I create for Arduino?

Hello, I have long dreamed of creating a library for microcontrollers, especially Arduino, that the world would like, but I don't know how, because some ideas have already been implemented, and some don't make sense, so I want to ask you. so that you can advise me on a unique idea for a library that will be useful. A library doesn't have to be simple, I'm not afraid of big projects. And right now I have a lot of free time.