I'm making a not so subtle reference to "don't let perfection be the enemy of good". A saying often said to people who are saying things need to be better.

To answer your softball, no, I doubt there was anyone who understood everything except petty early on. But very few people understand the whole OS let alone do any specialized task like data analysis, HPC, programming languages, encryption, or anything else. But here's the thing, the extra knowledge never hurts. It almost always helps, but certain knowledge is more generally helpful than others. Especially if we're talking memory but things like caching, {S,M}I{S,M}D, some bash, and some assembly go A LONG way