How do people figure out what they want to do after finding out the current job is not suitable/interesting enough?

Agree with Stacy and YJ, sometimes you just need to go through it / have that experience before you know what you want and dont want:

Is difficult to figure out what you want to do. But is simple to figure out what you dont like to do.

By knowing what you dont like. You narrow down your option.

In addition, how can you see the future of your job, is by looking at what your supervisor now. Because you are walking down his path. U-turn while you are still young, if you dont like it.