Ask HN: Do you have a customer discovery problem?

I’ve been bootstrapping a Saas company for over 2 years now and making just enough revenue to sustain. The product can be used for more than one usecase, hence I get people signing up for different use cases. And I’m finding it hard to figure out which usecase is the strongest. In other words, what segment of customers are getting the most value. I’m thinking if implementing a survey after users sign up but I’m not sure how credible that can be. Has anyone else faced a similar problem? What approach can one take to solve this problem?