You're right that food margins are typically 66%.

But this considers only the cost of ingredients. So you'd rather sell a bottle of wine for $15 (that cost $5) than sell a meal for $15 (whose ingredients cost $5).

On your final point, I suspect that delivery via Doordash or similar can take margin that a restaurant's own delivery service (via phoning in) would have made, and that Doordash has inserted itself as an intermediary (with a margin) where none was present before. The pie might be bigger but I'm not sure whether Doordash is capturing less than or more than 100% of the increase.