You can eat carbs, its not going to kill you as you said plenty of societies have eaten grains for a long time. The issues are more the glyphosate and other stuff they use to grow it, and mechanically separating the least nutritious part for white bread then bleaching it further. If you eat plenty of red meat, you can also eat bread its not a problem. I'll still be watching vitamin c, though most people aren't deficient. Most people are low in iodine, magnesium, vitamin D, and some other things though