That is exactly what it is. Don't spend your energy on something you can't change. Sometimes that is a good approach. For example, trying to get a single parent who is illiterate, mentally ill, or sick to help their child with homework in the evening is wasting time. It is an approach that won't work. I can see telling someone who keeps pounding that idea, "It is what it is." Other times that phrase is just used as an excuse to shut down all ideas. In my opinion, that phrase can be appropriate. It is all in how it is used and what follows next. "It is what it is. What other direction can we take to fix this."