Tubers like potatoes have been eaten since forever, those starchy foods that only humans (through cooking) and very few animals digest have been a staple since forever. Also, wild grains were consumed before that.
Yes but northern europe is only a tiny fraction of mankind, I believe most africans, asians and native americans are lactose intolerant.
This means that digesting milk is something new enough that the majority of mankind is not adapted to it. Also, lactose intolerance comes in various degrees and gets worse over age, so even people that don't have it might develop it.
I don't think that there is a mainstream backslash against milk, but if it would I think it would be scientifically based more than anything.
There is just so many scientific links between excessive consumption of cow's milk since birth to all types of illnesses.
Yes, some of us can digest it, but is it healthy food to be consumed every single day, under the form of yogurt, cheese, etc.?
Besides the high hormonal and fat content, it contains casomorphines that are addictive and are meant to keep the calf constanly next to the mother.
I think the idea that we were sold that milk is one of the best foods available and that it makes strong bones (it's actually linked to osteoporosis) is just pure marketing.
The food wheel we were taught growing up was in many places made by the food industry themselves, which I hope would be forbidden by now.
The official recommendations are adapting, did you see the latest food wheel from Canada? https://food-guide.canada.ca/en/