See it this way: Each subject you finished at university, did you come at the end thinking "I learnt how to program", or did you come out thinking "I learnt how to structure a graphics pipeline"/"I learnt the tradeoffs involved in building distributed systems"/"I learnt how to structure data to make consistent updates and retrieval simple and highly performant"?

The most obvious way you apply what you learnt in those classes is by writing programs that implement those ideas (And it's also the easiest way to evaluate whether you actually learnt the concepts). But you can just as easily apply that knowledge by designing systems for somebody else to implement — somebody who presumably lacks the knowledge required to architect the system. Hammering out code is easy, and you don't need a university degree to do it. It's the rest of it that takes some study.