I don't understand why people focus on gorillas when bulls stand around eating grass all day. Maybe, just maybe different animals are optimized for different diets. Most humans can get by and even be healthy on a vegan diet, though we're really more optimized to have a bit of meat every once in a while. Everything about us screams omnivore, and we're lucky enough to be able to go full vegan if we want to (take your B12).
Chimps and bonobos are our closest living relative, then gorillas. The chimp diet consists of 2% meat in the wild, but we've got 7 million years of evolution between us and chimps. Given that we've been cooking for at least 300,000 years (possibly as long as 2,000,000 years) and that we spent a lot of time hunting mega fauna to extinction, I'm gonna go ahead and say that maybe making cross-species diet comparisons isn't exactly helpful. I don't see no chimp taking down an elephant, but we killed off mammoths with spears and arrows.
But again, we're smart enough to construct a healthy vegan diet for ourselves, even if we're not purpose-built for it.