A lawyer friend told me that one of the key things he learned in law school is that his first jobs would entail cleaning up mistakes that old lawyers had made. It meant that old lawyers often made mistakes in basic things and, further, that he had to understand what they were trying to do. He wasn't necessarily applying new law. Rather, he was applying old law correctly. New law would come later.
So, this article, Beware tech career advice from old heads, make sense at first, until you remember that most people coming into jobs, tech or otherwise, will be working with legacy stuff. You have to understand the old stuff, such as the default date in COBOL, but do it better.