Maybe look at a Gorilla's teeth, who is almost exclusively a herbivore. It's pretty easy to see that big canines aren't synonymous with meat eating.
I think that a more accurate model to look at is gut length. Herbivores require longer intestines, omnivores are somewhere in the middle, and carnivores only require a short intestinal tract (shorter is better because there's a lower energy cost).
Eating meat is what allowed us to have a smaller gut, which meant that we could 'afford' to develop the large brains we have today.