I have a similar philosophy. If you can solve it once and the seal it away in a box and never look at it again ... then who cares. Write some tests or better yet hit it with a property test and then move on with your life.

I'm more worried about low quality code that takes the form of an api or object that everyone in the entire codebase has to use. Something where if it has a bug or if it needs to change, it will impact huge swaths of code.

Meanwhile, the code that takes a double and returns a double ... yeah it can be full of spiders and work by literal earth magic and as long as the unit tests are stable, I'm not losing any sleep.

If you have to change it just rewrite it from scratch and reseal away the evil.