The problem is finding a vector that pays for itself as you scale.
We see a problem and we think we've "solved" it, but if there isn't a scalable go-to-market business approach behind the solution, it's not going to work.
This is where engineers and other problem solvers so often get stuck. Industries and organizations and systems aren't broken because no one knows how to solve their problem. They're broken because the difficult part is finding a scalable, profitable way to market and sell the solution.
Take textbooks, for example. The challenge here isn't that you and I can't come up with a far better, cheaper, faster and more fair way to produce and sell and use textbooks. The problem is that the people who have to approve, review and purchase textbooks are difficult to reach, time-consuming to educate and expensive to sell.
Or consider solar lanterns as a replacement for kerosene. They are safer, cheaper and far healthier. But that's not the problem. The problem is building a marketing and distribution network that permits you to rapidly educate a billion people as to why they want to buy one at a price that would permit you to make them in quantity.
Sure, you need a solution to the problem. But mostly what you need is a self-funding method to scale your solution, a way of interacting with the market that gains in strength over time so you can start small and get big, solving the problem as you go.