"That product doesn't fit this market" seems originally just a polite way of saying "we don't believe you will ever succeed" without explicitly criticising the product or the people.
From an investor's perspective, it might be a condition for investing.
As a model, it's not particularly useful in that it only predicts possible success if a condition for success (PMF) has been demonstrated. And PMF itself is defined in terms of success ... so it's tautological.
I think the usefulness of it is in articulating that there’s no such thing as a good product in a bad market. A product’s goodness is defined in terms of its fitness to a particular market.
Not disagreeing that it can be a form critique, but it's true that a product built for one audience may not work out, but sold differently to a different audience may be a hit. It also may be the wrong thing for every audience.
When you don't have PMF, you either change the P or the M.
From an investor's perspective, it might be a condition for investing.
As a model, it's not particularly useful in that it only predicts possible success if a condition for success (PMF) has been demonstrated. And PMF itself is defined in terms of success ... so it's tautological.