I will not promote: How do I know I'm solving a problem?

Here's the thing. How can anyone know what they're doing is actually solving a problem? Does it really need to? From someone who comes out of college, how can you identify problems in the world? I understand that these issues that come to you are firsthand experiences. But how do you know that what you're building to solve this problem is what everyone is gonna need, and if the problem you're solving is worth it? I'm trying to think of something that people would wanna use. And I feel like I don't have enough experience in the world to identify an issue. Should I maybe work for a startup to obtain insight? How do you guys identify problems?