I think the main thrust is respect the code and understand why it was there. Don't start with the possible initial feeling that a particular piece of code or guard is not needed. If you do find that it's not needed, remove it or fix it.
People also tend to forget human and business impact. The code might look different if there is 1 week or 4 weeks given for implementation. Timelines, pressure from management/stakeholders to deliver faster has impact to made solutions and implementations.
That is when respect is needed - having empathy to understand why this part of software looks like it is now.
https://www.joelonsoftware.com/2000/04/06/things-you-should-...