It's not insanity. The specialists are the people building platforms, libraries, and tools. The idea of understanding multiple platforms is not a crazy idea like the author tries to convey.
I agree, I've met a few engineers in my career who believe working in more than one language is a bad thing.
Personally, I don't understand how people get by in web without knowing SQL and JS + some other language.
The idea that you don't understand the flaws that SQL can introduce into a system, and have little ability to debug them is baffling. How can you actually be productive when you only control a tiny fraction of your application.
