When it comes to knowledge there are different kinds of knowledge and different ways of acquiring each kind. On one side is theory and on the other side is the practical application of theory. Both types of knowledge are important and both make you better at whatever you do.
I think those who advance the furthest in life tend to be those who acquire knowledge at both ends of the spectrum and acquire it in a variety of ways.
Theoretical knowledge — teaches the why. It helps you understand why one technique works where another fails. It shows you the whole forest, builds the context, and helps you set strategy. Where self education is concerned theory prepares you to set a direction for your future education. Theory teaches you through the experience of others.
Theoretical knowledge can often lead to a deeper understand of a concept through seeing it in context of a greater whole and understanding the why behind it..
Practical knowledge — helps you acquire the specific techniques that become the tools of your trade. It sits much closer to your actual day-to-day work. There are some things you can only learn through doing and experiencing. Where theory is often taught in the ideal of a vacuum, the practical is learned through the reality of life.
Practical knowledge can often lead to a deeper understanding of a concept through the act of doing and personal experience.
Both of the above are important. You won’t survive in any career unless you can bring results and to do that you need practical knowledge. There’s no avoiding it.
At the same time learning how to solve a specific problem only teaches you how to solve that same problem again. Practice can only take you so far. Theory helps you apply what you learned solving one problem to different problems.