That's one lesson I drew from Is This Weird Vegetable Part Going To Be The Next Kale?. This proposed "next kale" is actually a byproduct of current brocolli production:
the answer might lie in selling a part of the broccoli plant that would normally be composted, not eaten. They’re calling it BroccoLeaf: The leaves around a broccoli crown that most people have never seen. “Before that crown has even formed, we go in and we harvest some of the younger, less mature leaves,” says Matt Seeley, VP of marketing at The Nunes Company, which sells the new vegetable in its Foxy Organic brand. “And that’s really what the BroccoLeaf is.”
Beyond being reported as less bitter than kale, it may actually be more nutritious:
Like kale, a single serving of broccoli leaves has a full day’s dose of Vitamin A or C. Broccoli leaves also have more calcium, more iron, and more potassium than kale. And arguably it’s also better for the environment—the plant is already growing broccoli crowns, so no more water or other resources are needed to harvest the extra leaves.
I'm a fan of promoting new things as a way of improving eating - e.g. The rise of Africa’s super vegetables and its promotion of not-widely-produced vegetables of African origin - but sometimes new food may already be hidden in plain sight. (It might also be worth noting that cabbage, kale, collards, cauliflower, romanesco broccoli, kohlrabi, and brussels sprouts all seem to originate from the same wild plant.