The counter point is that a field of corn or wheat produces far more calories than a field of kale. While the kale is healthier long term, the corn and wheat (as well as processing to reduce spoilage loss) reduces the cost per calorie, which is a significant contributor to a reduction in hunger and undernourishment.
Look at the statistics, today, Americans pay the LEAST for food in the entire world (25% less than the next closest, the UK), while consuming the most professionally prepared foods (eating out). — You read that right, Americans spend the least money on food of anyone while also paying to have it prepared the most frequently.
However, these advancements in production also bring problems, by lowering the cost of “low-quality” calories you reduce hunger but contribute to poorly balanced diets causing long-term issues.
there is a fine balance that needs to be found; if we redirect resources from, say, corn to kale, the average cost of a calorie will increase, (while the average cost for kale will decrease). However this will push up the daily price of 2000 calories that humans need, and may push that price up and out of the reach of some people.
As average affluence increases in the US (it is increasing, and has been increasing for all classes of people for a very long time) we may get to, or may already be at, a point where we can reduce our focus on the highest yield crops in favor of more nutritious crops without significant increases in hunger.