Matt Wensing makes a great point that product/market fit is only part of the objective. If the product/market fit is not profitable, it can be a very misleading objective.
If you summarize ‘achieving product/market fit’ as the goal, you may end up achieving a state wherein you have lots of customers but very little profit. As a result, you have lots of demand, and even lots of potential, linear growth, but you’ve settled for linear and you’ve settled for thin margins and you are stuck.
The whole article is excellent and very much worth your time, though the Hacker News thread about it is curiously devoid of comments - perhaps because Matt has said everything already.