Have you done all the marketing you can? Are you sure?

Has every person in the world who could possibly benefit from your product already bought it? Wait, let's back up to an easier test. Has each one of them even heard of your product? If not, what have you done today to make sure that they hear of it?

Have you identified each potential user of your application? Not just a general description of the type of user, I mean personally identifying information. Do you have their email address? Why not? How do you plan to get it?

How many people have seen your sales pitch and not bought? What are their email addresses? How many of them would have benefitted from your product? Why didn't they buy it? How do you know?

What can you change in your sales pitch to convert more of those views into sales? How do you know?

What can you change in your product to increase the population of people who would benefit? How do you know?

This isn't black and white, where things either work or they don't. This is the squishy grey area filled with actual people, who may buy (or not buy) for reasons that they don't understand themselves. If you think getting this "right" (think about why I put that in quotes) is faster or easier than building your product, then you don't even know how much you don't know.