vegan eating primate teeth look like cows teeth. Ours are quite different.
Our incisors are meant for cutting meat our front teeth for shearing meat off into bites, cut up by our incisors, chopped into small pieces by our sharper front molars and ground down by our rear molars.
And we have a highly acidic stomach full of protease for digesting protein - most vegetarian type species, ruminant type, have specialized bacteria in the gut to digest vegetable matter.
Cows don’t eat grass. They eat anything with carbs in it. The critters in their gut digest the grass.
Then the cows digest the critters!