Protein is what we need most of for the day more than any nutrient or vitamin. We were built with a necessity to eat meat and plus I don't have the heart to tell a lion and snake to eat tofu.
While we need more of proteins than vitamins (as we need vitamins in very small quantities), it is not necessarily derived from meat. Soy and hemp both contain as much protein as meat, then we also get protein from bread and other flour-based products, potatoes, lentils, beans, etc
If we actually were built with a necessity to eat meat, India would have collapsed.
Our closest living relatives, the other great apes, barely eat any meat at all. They get their proteins from insects, because they can't grow crops.
Lions and snakes are carnivores, humans are not.