A lot of people hate leftovers, and I think the reason is because they don't know how to store and reheat them properly. So the food dries out in the fridge from improper storage, or gets soggy/chewy in the microwave from improper heating. Or reheating foods in the microwave that should be reheated on the stove/in the oven/air fryer/etc. Or using the right equipment to reheat but using the wrong settings/time. I could go on and on...
The point I'm making is that there's no reason why leftovers can't taste just as good as when they were fresh if you know what you're doing.
There are a lot of foods that taste better and better with every time you reheat them. Especially a lot of stews: Grünkohl, Bigos, Lasagna, Chilli con Carne, Pörkölt, all kinds of Curry etc.
Problem with reheating McDonald's is, that it's shit food to begin with. To get a decent menu out of McD leftovers you put them in the oven for 7 minutes, but make sure to replace them with a pizza 6 minutes before they're done.
Yeah mcdonalds fries need to be piping hot and fresh straight from the fryer. Reheating in the air-fryer even right after delivery changes the flavor (though you can get them back to ideal texture which is still a big improvement).
The other night I put some leftover drumsticks in the air fryer and they were better. Also fried rice, better when it's sat overnight in the fridge first. Frying leftover potatoes with eggs. Leftovers are just ingredients.