"Changeable" is the key here. We coders are trained for abstracting things, but real world requirements sometimes change and your perfectly abstract module nee

"Changeable" is the key here. We coders are trained for abstracting things, but real world requirements sometimes change and your perfectly abstract module needs some non-generic functionality. Of course, there are software engineering techniques to solve these problems, but hey you didn't foresee these changes and now need to bill your client for these adjustments. So the trick is achieving a good balance between redundancy and dependencies. This is probably what seniority means in software development.