thats why cs courses has projects, to test the theories in to practice, the good thing about fundamentals is that it teaches you that the language its not an end for it self instead its just a tool to express yourself
My example would be: when was the last time you implemented your own merge sort?
True that my knowledge of algorithms benefits me, but maybe all I need to know is that it sorts an unsorted array.
In the end, the best approach most likely depends on the person. Some people need to understand things fully, at the lowest level before they can build on them. Others need to see something in use and be able to play with it to wrap their minds around it. I know I'm personally a combination of the two.
Regardless of the type of person you are though, I think everyone is advocating that you do something to get the ball rolling.
Learning to code, means being able to write a o(n^2) sort, not necessarily being able to tell why that algorithm is bad, or what O(n^2) means.