Good article. I have worked as a dev for over 10 years and have seen a LOT of really complicated spaghetti code that was only maintained by individuals in silos. Some used to joke about "job security" but I would rather my life not be a living nightmare unable to take vacation without keeping my work phone on me at all times because I'm the single person that knows how to fix a mission critical system. I've been there. It sucks for new people but it also sucks for the keepers of the tribal knowledge. It's exhausting.

Training, documenting, refactoring and replacing to eliminate that is good for everyone. If you are a good dev you won't have to keep tribal knowledge to stay employed.