Yeah, but after talking to a good number of people in a particular domain or industry, you'd have an inkling, though not guaranteed, what the core problem is and how you can solve it.

The discipline needed here, particularly by us developers, is to recognize the absolute core value proposition and to do just enough to validate it.

In the beginning, it might just be you and a sloppy script you write. No SaaS, minimal website. Your customer would have to email you to get anything done.

Once you get paying customers like that, you automate it gradually, and build out your SaaS.