Never had MREs.
Imagine a government bureaucrat trying to come up with K Rations.
The earliest ones were all dehydrated like that pork patty thing that sometimes appeared in C rations. Except every damned thing in it was dehydrated and largely inedible without water from your canteen.
So your out in some mosquito infested jungle sweating your ass off trying to nurse the water you are carrying...and to eat you need a good amount of water from one of your canteens to reconstitute your food from a dry powdery block.
After the First Gulf war they improved and made chicken ala king and rice dishes and stuff that was moist. But the first ones fully earned the scorn with which they are referred to.