The biggest problem with professional programmers entering the field is in my opinion precisely the lack of ability to reason about how given code meets the criteria you mentioned and how different versions of the code score using those criteria. Many people have a very hard time at all explaining why they choose to do something one way over another. You have to work on a single project for a long enough time to be able to see how your decisions from one year earlier affect the current code base to learn to do this well.