This thread may sound silly, but there's some truth here. Time you spend waiting for the idea is time you waste actually implementing an idea. PMF doesn't happen in your head, it happens when interacting with the market. Get something together, pitch it, refine it, repeat. You'll get there.
This seems like one of the best "right answers" to the "doesn't scale" problem. You can sell a product over and over. If it's critical to someone's business or well being (according to some definition of well being) then you can sell it OVER and over.