Find a problem you want to solve for yourself and then build a solution.
I created https://myhikes.org as my side project in 2015 because I hated the existing public trail platforms at the time - a lot of things have changed since then, but so has my skill set, data set, the way I write, the way I think about features, the way I weigh pros/cons of features and time.
Don't aim to solve the world's problems or make money with a side project, aim to make your own life easier or more enjoyable in some way. You never know what will come of it later if you continue using, building, and growing your idea.
I created https://myhikes.org as my side project in 2015 because I hated the existing public trail platforms at the time - a lot of things have changed since then, but so has my skill set, data set, the way I write, the way I think about features, the way I weigh pros/cons of features and time.
Don't aim to solve the world's problems or make money with a side project, aim to make your own life easier or more enjoyable in some way. You never know what will come of it later if you continue using, building, and growing your idea.