System Ops (at scale, large company, lots of teams) in a nutshell: you did not build the system or choose what kind, it was most likely installed using vendor defaults by the systems owner and you were called in because it's misbehaving. Most likely 50 other people have touched various parts of it, some with skill some without.

"Give me an IP, username and password - what OS is it?" are about all you start with and go from there. It's probably a critical system to someone, and everyone swears on a stack of bibles that nobody did anything, touched anything or made a change. You have very specific domain knowledge (kernel, grub, SAN/storage, systemd, dbus, etc.) and typically ask a lot of questions to the systems owner as your fingers are flying ruling out reasons (low hanging fruit common issues).