> seeing a piece of code that was specially written for a very narrow and specific use case, and needing to extend it to some scenario that the original author did not envision

There's pain in both options: making something specific that has to be made more general later, and making something overly general and never actually having a use for the additional complexity.

The former, though, is solving problems you have, and the latter is solving problems you often don't end up having. Given the choice, I would always prefer the former.