Fixing everything is impractical, but I'd say a safer rule of thumb would be to at least understand small strangenesses/errors. In the case of things that are hard to fix - e.g. design/architectural decisions that lead to certain performance issues or what have you - it's still usually not too time consuming to get a basic understanding of why something is happening.
Still better to quash small bugs and errors where possible, but at least if you know why they happen, you can prevent unforeseen issues.
Still better to quash small bugs and errors where possible, but at least if you know why they happen, you can prevent unforeseen issues.