From what I have read the diet of people in classical antiquity was only terrible for the very poor. Most people in ancient Rome got to, at least rarely, eat honey cakes and fresh fruit and dried fish and maybe once a year at festivals even a small chunk of meat. They grew chives, dill, garlic, asparagus, radish, parsley, thyme, mustard, cumin and many other spices. And they made vinegar and olive oil and garum (fermented fish sauce) on an industrial scale. Mostly these would be used as sparing garnish to the grain-centric diet. But usually present.

Citation required.

Medieval Europeans had several times as many sorts of herbs and vegetables as we do. I can forage 20-100 species on my block alone in the city; none of those species are in our markets.

Our supermarkets specialize in those that provide maximum bang-for-buck, including transport costs. That really thins the selection.