https://www.sciencealert.com/veganism-is-increasing-malnutrition-in-wealthy-countries
Im not saying we should eat meat all day everyday, we should definitely reduced it or stop that, but not eating any animal products does cause malnutrition (as by above source) and supplementing our everyday life with pills isn't exactly a great way to live.
Im ok with vegetarianism, im more or less myself, but vegan is something that isn't suitable for humans naturally.