Claiming that food delivery apps are purely rent extraction
at great expense to the restaurants that actually prepare the food


Your premise seems to be that the restaurants are somehow losing out.

The key though is that (if done right) all three parties (the app company, the restaurant, and the consumer) should benefit. The reason is that through economies of scale (delivering for multiple restaurants) and perhaps other factors, the app company is able to organize and execute the delivery at a lower cost than the restaurant would be able to.

One piece of evidence that all three parties benefit is that all three parties continue to use this arrangement.



Note that with certain countries and certain apps, the delivery app companies are actually losing money. Venture capitalists throw money at them hoping they'll end up as the "winner-takes-all".

Rarely though is it the case that the consumer or the restaurant loses from this arrangement. A consumer who finds this a losing proposition can quite easily stop doing business with the app. Likewise with any restaurant.