Omnivores are organisms that feed on both animal tissue and plants.
We feed on both.
Humans, like many predators, have forward-facing eyes rather than eyes on the side of our head.
The vast majority of humans practice an omnivorous diet and have been doing so for millions of years.
Humans are able to digest meat and absorb its nutrients, which we would be unable to do if we were herbivores.
Even our closest evolutionary relatives, chimpanzees and bonobos are omnivores, they just don't eat it very often. If there is no meat they won't eat meat and therefore live herbivorously.
We can eat a diet that consists of only eating animals and be healthy, a herbivore species cannot do that.