In an ideal world this is true. But in reality we don't always have control over the codebase from birth until deprecation. Often, you find yourself a newcomer to code, and being able to reason your way though it can be time consuming, and scary.

I think this article's approach is a good one. Take precautions, use things like continuous builds, static analysis tools to boost your confidence, but DO make the necessary changes. Better sooner than later.