The reason I used to think this is like other technically orientated founders. If I build for a market that doesn't exist then you are playing lotto. It's not even good odds, you are better off playing 0dte spx coin flip.
What you fear you build for and if all you have are unknowns then you are going to simply end up building everything lose differentiation and your potential customers even if they find you will walk
Despite classics like the SBF article that was taken down, this framework is quite good but the best thing to do as bootstrappers is to focus on generating net positive cashflow as soon as possible not running a PMF search engine which requires lot of minds and capital injection.