Is anyone else suspicious that this generic label of "Ultra-Processed Food" is being applied broadly without really bothering to address actual causes?
I'm not suspicious. I recommend reading books by Robert Lustig, Gary Taubes, and Chris van Tulleken. Note that I'm not advocating just accepting everything they say - some of it is controversial for good reasons, and some of it is probably just wrong. But for me there's more than enough logic and sense in them to result in some pretty compelling suggestions for causal mechanisms.
For example, is it high sodium, high saturated fats, or just high caloric content in general that's the issue? All of the above and in combination, I'm sure, but this seems like a condescending and misleadingly simplistic way of communicating that.
Not really - especially the "high caloric" content. The bomb calorimeter - with its suggestion that all calories are equivalent - has caused untold harm because it's overly simplistic to the point of being fundamentally wrong. For example, I can consume a stupidly high number of calories per day from fat; but if I get enough-but-not-too-much protein and a very limited amount of carbs, I will lose weight and be in good health. Many people on such diets have actually reversed arteriosclerosis; the calcium portion of the arterial plaques always remains, but the pus-filled blood-clot sacs shrink and disappear, and the likelihood of heart attack and stroke is drastically reduced.
Further, it reeks of the naturalistic fallacy... It's not the fact that it's "ultra-processed" that makes it unhealthy to consume, but the ingredients... right? Surely a food can be ultra-processed and also healthy?
I totally get where you're coming from, and I support your skepticism. But if this is something you care about, I recommend a dive - both wide and deep - into the available evidence and theories. I think you'll be surprised at the complexity.
For example, let's look at your last question. One of the things that ultra-processing destroys is an almost-mechanical property that changes both the rate of absorption and the total amount absorbed. For obvious reasons, this alone can make the difference between being good for us and being bad. Apples are good - apple sauce - sweetened or not - is NOT so good.
Also, you may see things like carageenan, lecithin, carob bean gum, guar gum, and a multitude of other emulsifiers and smootheners. Many of these are entirely natural and exist in small quantities in fresh foods. But when they're separated from their sources and added in large quantities to things like chocolate milk - to give them that smooth texture - they also start to emulsify the mucus lining in the gut. This disrupts the gut microbiome, and can also allow things into the bloodstream which a healthy microbiome normally guards against. That 'stuff' that doesn't belong in the bloodstream can have nasty effects, perhaps the least harmful of them being increased inflammation.
To be sure, there's a lot of nuance here. But there's increasing evidence for the contention that 'ultra-processed' - vague though it may seem at first glance - is in fact a pretty good yardstick for the healthiness, or lack thereof, of the food we eat. I think ultra-processed food is a real, serious, society-wide health threat. But please, don't take my word for it. Do some digging, and if you feel that I'm wrong, get back to me and we can discuss it some more.
PS Even the 'saturated fats' thing has a lot of subtlety. Olive oil is such a fat, but consumption of fairly large amounts of it is part of the Mediterranean diet, which doctors recommend for good reason. There's even some suggestion that beef tallow is a healthy fat. But trans-fats, or other similarly modified fats, seem to promote inflammation and contribute to arteriosclerosis. And don't get me started on the whole cholesterol subject. Some of it is good and even necessary, some of it bad, and the goodness and badness may be conditional on a bunch of factors. There's probably enough nuance there for at least one good doctoral thesis.