If you repeatedly hear any of the following comments, chances are you are not solving a critical problem:
1. “If you made your app easier to use I would start using it.”
2. “I’m really busy right now but I’ll start using your app soon.”
3. “If your app was cheaper I would start using it.”
(1) David Cancel says that this feedback indicates you’re not solving a critical problem. I’m not sure the problem needs to be “critical”; perhaps it’s enough that the customer has a “Job To Be Done“.
(2) Cf. What problem are you solving?