Every 'primitive' (I prefer original) group had a diet that placed great value on meat, even if there was very little. However, all animal products have this same effect. The ancient Swiss and other groups from the Alps survived primarily off of dairy products, simple rye sourdough bread, fresh greens during the right season, and very occasional meat, with a focus on organ meats.

The most healthy groups focused on animals products. The African tribes that subsisted on animals did so almost entirely on cattle blood and the products from it. The ones that had greater amounts of plants in their diet were dominated socially and physically by the tribes subsisting in animal.

Other groups, such as Malaysians and Polynesians, used jungle products and subsisted mostly on seafood.

In short, you are correct, only all animal products are important, not just meat. The modern system of primarily plant based agriculture for consumption is both unnatural and unsustainable. These products are easier to manipulate, store, and produce, and this is why Big Ag and the government are so obsessed with preserving this awful system.

Btw, monoculture systems are really inefficient. Most of the crops produced today are for feeding animals and ethanol/biodiesel. We would use 1/3 (yes, one-third) of the land to produce the same amount of animal products if the land were in permanent pasture. 60% of the corn produced today is used for ethanol. So when seed, fertilizer, and chemical companies use "feed the world" as an excuse to increase production, know that they are lying through their teeth. There is plenty of food in the world, but it isn't sent to where it needs to go because it isn't profitable.