I wouldn't say useless exactly but probably not needed all the time. Much of it you can likely make up as you need it and that's something we talk about in the book and the preview. Things like speed, senses, languages, and the like you can fall to "whatever makes sense given the story of the monster". That's sort of antithetical to the defined mechanics of 5e but it works fine in play. I'm not sure I'd want a book of published monsters to be that sparse but it can certainly work for a home game!
