Right. I think we kept some of the ability to detoxify some plants from the herbivorous apes we descended from, but then we spent millions of years scavenging (probably eating a lot of brains as we could smash skulls of lion kills open with a rock), then hunting, following migratory grass eaters
Plants became emergency food. We're not as good at detoxifying them as a gorilla is
Hunter gatherers universally (outside the wet tropics where fruit is plentiful year around) eat meat when meat is available, and only use plants when the hunt fails
We classify animals as obligate carnivores when we see them in wild eating only meat. When we have found humans in the wild they eat only meat. If you study pre-agriculture bones you find they had a practically all meat diet.