Great question! I think about this as a matter of generalists vs. specialists.
Some people find a topic they love more than anything else (physics, poetry, gardening, marketing, etc) and want to master it. So they spend all their time learning about it. Let's call these people specialists.
Other people are interested in many things, but get bored when they try to go too deep on any one topic. Let's call these people generalists.
The good news is that both types of people can be very successful!
It sounds like you might be a generalist, so let's focus there. If you're a generalist, one of the best things you can do is stack skills and find links between different types of knowledge. Let's say you're interested in business. You may not be interested in learning everything there is to know about marketing, but you can explore it a little bit. Then you can learn a little bit about business strategy, management, accounting, etc (these are all just examples.) Over time, you'll be building a stack of skills that become quite valuable. You're flexible and you're always open to learning more. You're not the best marketer, but no "master marketer" will have your unique blend of skills.
Second, as you build your skill stack, you can learn how different areas of knowledge fit together. A marketer who also gets strategy and understands how to manage people can accomplish far more than someone who just knows marketing. And as you build these knowledge links, something amazing happens - you change the way you think about problems. You get better and more flexible.
So how do you do this? Just love to learn. Particularly outside the classroom, read widely, explore what seems interesting, and check back to see how your growing body of knowledge complements and strengthens what you already know. You will naturally gravitate towards what seems interesting, and you'll develop an insatiable curiosity that will stay with you throughout your life. You won't know exactly the same things as everybody else, but what you will be is unique and valuable.
Hope this helps! Good luck!