I don't agree that's the hardest problem. Most people want something that solves a problem, and if you see a problem that lots of people have it's not too hard

I don't agree that's the hardest problem. Most people want something that solves a problem, and if you see a problem that lots of people have it's not too hard to think up any number of solutions. The really hard part is finding a solution that most of those people think is better than the problem. So many solutions simply push a problem from one area to another (time to set up, cost, annoyances, etc.)