James Sinclair argues in a short talk that product–market fit (PMF) is determined by customers, not founders. He explains that PMF is evidenced when people sign up, pay, and would be significantly unhappy or inefficient without the product, and notes startups may take years of iteration to reach true PMF.
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I think for startup founders who are thinking about product market fit, and if you haven't worked at a startup before, if you haven't been part of a team that's delivered a product, if you haven't had people around you talking about how to understand, measure, define and what it is, one of the things that's so important our product market fit is you don't get to choose it, your customers do. And what I mean by that is you're going to build your mvp, you're going to go to market based on this hypothesis that you can deliver sufficient value. But ultimately, if people sign up, if people are willing to pay for it, and if not having that product would impede, interrupt or cause inefficiency, and they would be significantly unhappy to not have it, that's product market fit. And very often you won't get it for years. So you might get a little bit of it, some traction, some value, you'll see some churn. You make your product better, you iterate on it. So you can have kind of PMF. But there are many companies that will go 3, 4 years till they actually get it. Your customers choose PMF, not you. Good luck.