In general true but sometimes it's almost impossible to prove that it is actually unwanted or plain wrong and you need to take some risk for the bigger benefit.

In general true but sometimes it's almost impossible to prove that it is actually unwanted or plain wrong and you need to take some risk for the bigger benefit. It's not something to do lightly but it is actually needed sometimes. Our application has bits that hasn't been touched in years and no devel exists with experience in the said (problematic code) and if new development is needed and if that bit puts the new work at risk sometimes you have to make some judgement call and take the calculated risk.