This is why I still like old Unix systems (early BSD/v7 etc). It is possible to get a complete understanding of the system in a relatively short amount of time and they're still pretty productive.

xv6 reflects this from an educational perspective: http://pdos.csail.mit.edu/6.828/2012/xv6.html

I think we now have to settle for "a pretty good understanding of a lot of things, just never the things you immediately need."

Reading the link felt like watching a movie that gets interesting and stops midway. I wanted a bit more, i hope the author expands on the article & turns it into a longform one.