I had a new but pro-level published and well-reviewed writer go over an MS of mine, and he highlighted every instance of "Was/is" as passive, and every instance of passiveness as something to be rephrased or deleted. Including the phrase, "He was human." (yes, in that world, it had to be said and couldn't be assumed). You could tie yourself in knots trying to figure out how better to state that one quickly, efficiently, and above all, in a way that's *invisible to the reader*...
I knew I could and should switch the phrase "He was red-haired") to something that came out in the course of natural action or at least less-bland descriptor, but letting a reader imagine a character I know is a carrot top as a brunette doesn't change anything essential. But humanity? It wanted to be stated up front in the fewest words.
(That being said, all of his broad-view advice was superb, and most of his more pointers of "This scene drags at the opening" were equally excellent or at least correct.)