For the overwhelming majority of history, the overwhelming majority of humans have gotten most of their nutrients from plants.

There are tens of millions of healthy vegans. Not everyone can be healthy on a pure vegan or even vegetarian diet, but very nearly everyone can do just fine on a couple of meals a month that involve cows, chicken/duck once a week, and an egg every day or two.

If you need large amounts of non bean/grain/hemp protein for some reason then chicken is still vastly better than beef, and insects are totally an option.