I agree basically with what you said. I don't eat meat though, and have noticed a change in myself since stopping (again)...more on that in a bit.
Sugar and fructose being a prime example. Far from being in most everything that is commercially available these days, this stuff would be a rare treat. Certainly, at a basic level, it would be something that is consumed along with fibre (what some call the antidote to sugar), just as nature intended.
Sugar and fructose, IMO, is a lot more healthy than consuming all that "low fat" "fat free" "no sugar added" "low carb" crap they're pushing which is filled with poison *inserts finger in mouth and pretends to gag*
Pure, unprocessed, unbleached sugar is the kind you want to consume. It looks brown, sometimes comes in a stick/stalk/cane and sometimes smashed up imported out of Mexico (or other places) similar to white sugar. Kind of pricey, can't afford it all the time, but when people can get it, I think it is a preferred sugar intake than the other.
Would people not be able to garden during this time? Hot pack jars by boiling them? If so, that would bring back the farming methods, it would still leave the processed part of it out though (you process it to jar it, but not in a factory where god knows what goes in it too).
Also, in some areas... nuts and fish and the likes would not be available. Where I am at for example, I have seen very few nuts just growing, even in the mountains I have come across very few. And the only place off hand that I can think of for fish is a lake nearby where the fish are brought in and grown basically, they look like giant gold fish. So forging in this area would involve lots of bark, edible weeds, and water (if you're lucky and the stream isn't dried up)...you could of course hunt, we have rabbit, deer, bird etc... for those that eat meat and would do that.
What I have noticed with consumption of meat from the store here in my area. There is A LOT of hormones in it, and who knows what vaccines. While eating it there is increased moodiness, tenderness in the breast area, breakouts of acne, etc... When not eating it, that dramatically drops. If milk is removed from the diet, all of that basically disappears. So even if a person stops eating meat and dairy, hormones balance out and there seems to be less side effects (at least for me).
I don't know if that made any sense or if it's just random babbling, but that's my thoughts.