Modern apes are still frugivores, about 20% of their diet comes from fermenting leaves, but its not a significant percentage.
I specifically mentioned gorillas as the species is classified as predominantly herbivore, with fruits making up a very small percentage of their diet.
If an extant species has this specific diet, it is at least plausible to conceive that ancestor species had it as well.
Humans are mono-gastrics, but not a hind-gut fermenter, the bulk of our nutrition by our but biology is going to be meat or fruit, and we can't live on fruit alone.
That would be the case if the species was intaking food raw, which is not the case. Cooking of food facilitates the access to nutrients in it, both for vegetable and animal source.