You certainly do! The variable we tend to be rigid about is whatever our idea of expectation is for our progress. It’s worth it to you and your employer both to be well organized in the way you approach legacy code. If you’re actively turning rotten stuff into tested, reliable code then you can organize yourself in a way that doesn’t require you to eat the whole elephant at once.

It may take some creativity, and I won’t claim this is universally true, but in all but the most exceptional of circumstances understanding of even an ugly codebase can be accomplished in bite-sized pieces.