How is a delivery service unproductive? Division of labor is one of the most fundamental principles in our economic system. You being able to do it yourself in your free time doesn't make it unproductive. You could also make your own clothes, that doesn't make the clothes industry an unproductive endeavor.

You are correct, and the problem is an embarrassing lack of understanding and imagination on the part of the people criticizing you. An entire car dedicated to delivering one meal at a time, directly to the recipient, should be exorbitantly expensive to cover labor and resource costs for the driver; the artificially low prices customers pay are borne by drivers, who see essentially zero return in the long run when their profits are netted against vehicle costs.

What actually works is delivery of multiple orders to a semi-central location for last-mile pick-up by the customers. In a sense, this is what restaurants and grocery stores are. But to retain the variety, readiness, etc. of delivery, obviously some new solution must come around.

You state things as fact without citing a reason.

For the person getting the item, it is [extremely] productive.