Truth be told, a significant portion of my day job is still web application stuff. The web, whether that's HTML/CSS/JS applications or APIs, is inescapable at this point for a huge portion of programmers. Only the lucky few get to hack on databases, hypervisors and file systems for a living!

But, armed with the knowledge of sockets, processes, etc. and how this correlates to performance/scaling, I've been able to carve out roles where I get to spend a decent amount of time working on problems that I get excited about.

But even before I was able to work the knowledge into my day job, nothing beats the dopamine rush of learning things that fascinate you! The rabbit holes that learning the basics of Unix have opened feel like they could occupy my hobbyist hours for the rest of my life.