Humans have relied on bread, pasta, rice, and tubers for most of their calories since time immemorial. Japanese people eat plenty of rice even today and they are very healthy.

"Food pyramid dumb, eat meat" is a very reductive take.

Folks had to do the harvest and milling work themselves until recently, it’s not the same. Nor are the quantities.

Only the last hundred to twenty thousand years or so. Evolutionarily speaking, that's not our typical diet. Maybe excepting tubers.