Don't feel bad. Nearly all the critical systems for computers I generally represent at least 1 person's (sometimes many peoples) life work. You can't possibly understand every aspect of everything program your computer uses.

I suspect there is not a single person in the world that fully understands every aspect of GRUB, SSH and systemd. There is simply too many fine details in these things to understand everything.

No need to feel bad. Your biggest power is the one you take for granted: your ability to Google and educate yourself when needed. Many people can't do that effectively.