People have lots of pain points that irritate them enough to pay for a fix, but the vast majority will not frame it in such a clear way or just announce it to the world.
You can take a course like 30x500 (my personal recommendation) that equips you for such a pain discovery and fix definition process. If you're willing to be patient about it, you can also, on your own time, develop your listening skills for that sort of complaint.
Example: from your question, if I could offer a service that lists points of friction or inefficiency that many people complain about and would pay to improve, you would probably pay me to use it and pick a starter for your project. That's a business idea! If I can figure out a reliable, sustainable way to gather this information and then reach out to people in your situation to offer it, I'm on my way to a viable product.