I recently met several 'carnivores' who eat one to two pounds of meat every day, and only meat, dairy, fruit, honey, and water -- no other carbs, no sugar, no rice, no pasta, no bread, no wheat, no corn, no veggies(!) (apparently a lot of vegetables have something called "oxalates" and that's bad, though I know nothing about the topic), no alcohol, no nuts, no seeds, no seed oils, etc. They swear by it. I'd imagine that carnivores can probably estimate their red meat consumption very accurately, though I didn't ask the ones I met recently -- they were pretty sure of how much meat they eat each day, so I assume it's trivial to x365 to get "how much beef they had in the last year". Well, maybe not that trivial because some of them also have pork and chicken?
Carnivores are a fairly recent phenomenon.
The studies linking meat to health issues were done on the McDonald's and coke population.
There is also zero commercial interest in pushing meat over carb filled diets.
Look inside any supermarket. It's literally 95% non-meat processed food with long expiry date, an easy manufacturing process and the added benefit of keeping people addicted and hungry.
https://www.google.com/search?q=carnivore+groups