Agreed, there's such a wide knowledge gap between "I read about this language design choice online" and "I know this from first principles". Truly, thoroughly understanding the languages and tools you work with every day unlocks a deeper level of understanding that you can't substitute with anything else. It's what people often describe when they first learn Lisp, but the same actually holds for every language, tool, etc. There is tremendous value in depth. However, since there is considerable opportunity cost in choosing what you put your time and effort into, do be mindful of the tools you decide to acquire this amount of knowledge in.