How do you know how much, or what, we all eat? Was there a poll taken but I didn't see it, or what.
Yes, macro nutrients are important, especially protein. I do think that insufficient protein can probably cause serious symptoms in people who are carefully to get all their other (micro) nutrients (minerals, essential fats, etc.) Protein is the deal breaker. It's not everything, but it's mighty important.
However, if you have eaten tons of mainly animal protein for 40 years, then go on a cleansing diet with low protein and lots of fruit & vegetables for perhaps a few months, your health will probably improve. But you have to know when to stop the low protein regimen.