Hard disagree. I think a huge part of our job as engineers is to build systems that can outlive us and comfortably change hands (without the next team cursing the former).

Maybe this is born from spending so many years in Amazon (with it's high turn over and near-quarterly re-org shuffling), but what's getting called "replaceable" here I'd call "writing maintainable software."

The goal is to get knowledge out of your head and into the codebase so everyone can reap the benefits. Knowledge hoarding is lame.