It’s funny, I have seen so many UX Designers not take criticism well. They often default to place all the blame on the client/product owner.
Design Principles are a set of statements that communicate what we want from a project or product. It’s a way for everyone to agree on a couple of core principles that the work should be measured by. By determining these ideas early on, you create a framework that will help you take design decisions and give constructive feedback.