The ratios in which they are given is not what we have evolved to process, though.
As I said above, it's like vitamin supplements.
Eating the food itself is still better.
But it is not like other foods don't have protein. Even grains have protein. What about the grand total?
Second, what about the lifestyle? We don't have the active lifestyle of hunter gatherers and we are not pursued by lions anymore. Do we still need all that extra nourishment?
Also, the environmental impact. When we evolved, we were not farming or building factories. We were running around like the rest of the animals trying to get food. From what I read, the amount of energy and water required to process meat for the population today is a huge burden on the environment, which we did not put when we were evolving. So, what is the really the "best" for us long term?