1) Not all vegetation is fibrous. There is high fiber greens such as grass and low fiber greens such as lettuce.
2) Vegetation is 90-95% water. Where can I get 2 liters of water per day without the tap?
2) Mammals have bitter receptors on their tongue. Raw spinach/grass is bitter and freshly picked raw lettuce and other greens are sweet. Follow your instincts. - Evolution of Bitter Taste Receptors in Humans and Apes
3) We have a bigger brain and smaller mouth. Hence the intelligence to properly chew the non-bitter edible leaves and a feeding restriction of a small mouth which forces us to properly chew the food. Gorillas are too stupid to chew their food properly and just chew it a couple times and then gobble it down. Cows on the other hand regurgitate their food and chew it over 150 times to break down the cell walls. Bacteria cannot break down cell walls, if they could, trees would start to fall.
Carnivores? Where can I get magnesium, calcium and vitamin k? Should I start grinding down bones?
The science tells me omnivores and it tells me that paleolithic humans ate a boat load of edible leaves. Hence their large bones which is the result of their high intake of minerals.