Delivery is not as heavy as a cost as running the kitchen itself. I think food production is so overlooked in these discussions. The operating cost for a kitchen is insane, labor, ingredients, storage, inventory, etc...
Peter Thiel always uses restaurants as a good example of a business model that is so costly that there's no margin left, combined with the impossibility of a monopoly. So you take something that's already tight on margins and you make that even tighter with delivery.
I'd be curious to know if any of the food delivery apps have incentivised delivery to grouped buyers. e.g., $10 if someone buys, $8 if 5+ people in the same street buy, etc. Encourage delivery efficiency and also delegate marketing to word of mouth.