The reason SQL is great in my opinion is partially what the author highlights. In addition I think one of the reasons is that it is a very mature technology tha

The reason SQL is great in my opinion is partially what the author highlights. In addition I think one of the reasons is that it is a very mature technology that baked over decades. I first was exposed to ANSI-92 SQL in school and that was already like the 2nd or 3rd revision of the standard. I used it in my first couple of jobs and the skill applied everywhere, Oracle, mySQL, SQL Server and there was even something called Access that understood it and Access was widely used amongst small businesses. Knowing SQL to me was and even now is extremly helpful to understand data and how to tackle data problems. There weren't many other technologies that had such profound long term applicability, besides maybe knowing and understanding HTML and C. Many new things are just variations and improvements of those core technologies, and those can easily be understood and learned with good foundational knowledge.