I don't know why so many people think this is the case and then hate on the product.
Taking too much of any one thing is bad for you. People were doing only-soylent as an experiment. But for the most part 90% of the time I've read people only using it for a single meal each day, or on days they dont have time to cook, and eating regular food otherwise. Which sounds entirely reasonable to me, especially given how often people substituted those moments with junk food.