It's not only about packing. If you take your first bite a minute after a dish is ready in the kitchen, it leaves a much different impression than the first bite you take after 10 minutes in a ride. The extra time spent in the delivery is always going to make a huge different in how the food tastes, at least for certain dishes (dumplings, e.g.).

Yeah. I think if you got delivered a hamburger in a restaurant that had just been sitting for 15 minutes, not under heat lamps, you'd be complaining to the waiter. I think we sort of internalize that our food is going to be getting colder etc. as the process of eating it goes on and we don't really think about it. And, as I noted elsewhere, something like soup dumplings or dumplings generally (unless you pan-fry them at home) are going to be pretty meh too in general.

A restaurant burger is a different beast than a fast food burger. Restaurants usually go for big thick patties, softer breads, and may go with more soupier sauces. A fast food burger is very thin, on a more serious bun and usually has less moisture on it overall. Even the actual burger meat itself can be different, with fast food being a fattier cheaper cut and restaurant burgers being a fancier ground beef.

And yet it still tastes good hours later as leftovers.

If you keep the bread from getting soggy, which is definitely possible (worst case pack it separately), a delivery burger can be high quality. I don't care if it's no longer perfect.