Indeed plants had such a big influence on how the human race evolved, and on the other hand our farming activities also exerted evolutionary pressure on which plants became more diffused. I agree also when you mention that we don't always harvest the most nutritious plants but farmers are not dumb, as everyone they respond to incentives, in this case governments give many incentives for certain crops, this decreases the prices of food that reaches our tables but on the other hand we are incentivizing farmers to decrease the diversity of their crops, there is much to say about this topic