I can't really speak to the exact sodium content, but it's more than reasonable for emergency rations or hiking or SAR. You're not eating this stuff every meal for the rest of your life, and if you are, you deserve what you get.
It also gives you a lot more control over portions, which can be an issue as well. There is no point packing more than you are going to eat.
I brought up the salt content not for health reasons, but taste. Many of the ones I've tried have been so salty I've had trouble finishing them even after a day of backpacking.
So sure, you can combine your nutrient goo powder into a single sack, and thereby save a tiny fraction of the weight of the food (and water) itself. But you're splitting hairs.
I picked a mountain house pouch-based product at random on amazon, and the packaging weight was .06oz on a gross of 5oz, or 1.2%. Which is, of course, nothing. I have heard exactly zero people, ever, complain about the weight of their dried food packaging. I've heard lots of people complain about camping food being boring and flavorless.
If you like Soylent, fine, but the claim that this stuff is the obvious best product for campers is silly.
If I'm carrying a stove, then I'm carrying fuel too. That weight and space adds up. Even if I'm carrying my MSR Windburner, it's still about the size of my first aid kit. My old MSR PocketRocket was smaller by itself, but required a mess kit or a pot of some kind for the hot water. I could go with a soda can alcohol stove, but then if I spill my fuel I'm a bit boned and they aren't always the most reliable or efficient setups to begin with.
Soylent is: remove Soylent package from pack, dump approx 10 oz into Nalgene, add water (cold, filtered from a stream if possible), shake, and continue.
Cooking while backpacking is fun ... sometimes. Once in a while it's nice to take the time to put together some backcountry gourmet stuff.
But for just having the equivalent of emergency rations in my pack, Soylent really is better than the other choices.
Oh, and anecdotally: digestion is a pretty big deal when you get far enough away from civilization. I've had some Mountain House meals do some pretty unhappy things in my gut, and there's only so much cleanup that small wad of "oh-no" TP I carry around can do. Soylent tends to digest really well and not cause post-digestive messes. Unless, of course, you happen to be one of those many people who were allergic to one of their recent formulations.
I can also state that the majority of people I know care so much about weight that they would never carry mountain house type food around.
If we both extend our friends to the general public, we have a clash. Or, maybe, there are different types of people in the world, some of whom think that Soylent is a great alternative for many of the situations they find themselves in.
