I know this may not answer your question, but I would suggest to flip your thinking pattern.
By creating a solution that's looking for a problem, you're likely to not add much value to a prospective customer.
Instead, look at some of the problems and friction points in your own life, and see if you can create a solution to those problems.
Worst case scenario: you make your life easier, even if you don't make any money.
Best case scenario: Other people have this problem too, and might pay you to solve it for them.
I earn my money selling my skills to people who think they're going to make money from making a website.
My logic is that - During the California gold rush, pickaxes sellers fared much better than gold miners.
Edit: I've had various personal websites for decades. They haven't earned me a dime, directly. But indirectly, they make an amazing professional portfolio.