The best way to truly know how your customers feel about your app at scale is with feedback.
A simple answer, but critical for every mobile app. You need your customers to talk to you about your app. It is important to find out what's wrong with an app or what could be improved before learning about an issue via a review left in an app store. The app stores are no place for a conversation; in fact, they are more of an invisible wall between you and your customers. You can see what's wrong, but you are blocked from communicating with them to solve the problem.
It should be as easy for mobile customers to talk with you as it is to use any other feature in your app. The more easily you are available to get in touch with, the more likely they will reach out. Today, everyone feels entitled to be heard therefore it is important to make it easy for customers to use their voice. Let them know that you want their feedback. When you receive feedback, show the customer your appreciation.