Every plan has flaws. If someone presents a plan to you, it’s definitely helping them to identify flaws in their plan. When you do, though, distinguish between fatal flaws and fixable flaws. Does the flaw you’ve found mean the plan should be thrown out entirely? Or does it identify a way to improve the plan? What I’ve seen most often is that someone identifies a fixable flaw but it’s heard as a fatal flaw. This does not tend to be an enjoyable experience for either party.