Sure, we used to do that lots back int he day before freeze dried foods really came along. You will probably need to boil them or let them steep fro a long time and the water/food ratio has to be good or you can end up eating crunchy stuff or soup.
MH is the best I've tried, and I've tried plenty. The ease of use is great on backpack hunts- boil water, add to pouch and wait ten minutes, eat from pouch.
You can also add instant mashed potatoes to bulk things up. (with more water of course)
Lipton sidekicks also need to be cooked, which is a drawback
It all depends on how much weight you want to save and convenience. For instance, lets say you are using MH compared to Liptons meals. You need a small kettle or pot to boil 2-3 cups of water, that's it. So you save carrying the larger pot and you carry less fuel for your stove too. Plus the MH are very calorie dense.
Tinned fish or meat you are carrying lots of water and metal weight. Then you have to burn out your tins and pack the garbage out, too.
Much of this depends on how long you are going for, what type of terrain and how many people you have. More people= spread the gear out. Longer trip you need to carry more food so need less weight. A weekend backpack hunt over moderate terrain? hell, take the kitchen sink. 10 days in steep goat country? Weight becomes critical.
People complain about the cost of MH meals, and they are not cheap but can be really a small part of the expense of a trip, especially if you have them for dinner and eat more standard stuff during the day.
But hell, in the 1970's and 1980's, before all this newfangled stuff, my brother and I and our group would spend 10, 14, 20 days living out of a backpack in the BC wilds. Back then it was oatmeal, trail mix, landjaegar sausage, jerky, crackers, powdered eggs and potatoes, pancake mix with sugar and then we had a few of the aforementioned dehydrated meals. before we bought a dehydrator we would go to bulk food places and get bags of dehydrated foods, and then mix them together in ziplocs to create individual meals. Tjere were books that outdoor stores sold that even had recipes for this sort of thing. The drawback with them was of course- need lots of water, a big pot, fuel and time. But back then we had lots of time and we built fires to cook on, only using backpacker stoves for the occasional quick hot lunch on a rainy day or if we were weather bound in our shelters for a couple of days.
MH is waaay easier though.
