The article discusses a way to test product market fit prior to launching. After launch its obvious. But then the way it tests product market fit is asking its users if they would be disappointed if the product didn't exist.

But if you have users you can simply test product market fit to see engagement. If people are engaged, that's a good sign. If you have people that are signed up and aren't engaged, that's a bad sign.

The author uses Slack as an example of a company that has product market fit and over 50% of users surveyed would say they'd be "very disappointed" without Slack (the magic number to beat is 40%). I wonder how that poll would fare for Microsoft Teams, that has 320 million MAU compared to around 40 million for Slack (roughly, few years old but order of magnitude is ~10x). Does Slack have more of a product market fit than Teams because very few people would be disappointed if Teams stopped existing? Or is usage a better metric?