Earlier quoted context omitted.
Once meat is eradicated in the name of agricultural efficiency, non-grain, non-bean vegetables will probably be next on the chopping block.
You have a point here, yup. Some vegetables are luxury food, and less efficient than cattle. Replacing nature with monocultures is a problem. If we stop eating cattle for that, there is not moral room to keep eating chocolate, for example. Or coffee
Optimizing diet for land efficiency probably does not produce healthy diets. You can find strong evidence for this trade-off in the changes of average human health at the advent of agriculture.