But that usually happen when a new engineer just out of the university start tinkering with "optimizing" and existing code base. They are usually greeted with a minefield of things that they thought where inefficiencies and turn out to be workarounds. Making the new and "improved" code break already working systems.
This is so so true. An actual real life engineering meme that I am super tired of. Hearing everyone around you !$%*! about other people's code is no longer the hip nerdy commiseration it once was. Now it's just an overplayed geek cliche that has worn a rut in my ears.
It seems I made a wise choice a few times when I extricated myself from projects with especially bad code bases without trying to euthanize them. Come to think of it, remaining members of those project teams did often look like zombies.