I think the problem with public recommendations is not that they are wrong or right but the fact that most people do not follow them. They follow basically what the large food concerns put in the food shelves. Which is typically highly processed food with a lot of sugar, fat and salt.
A lot of people actually do follow them. If you check https://fns-prod.azureedge.net/sites/default/files/nutrient_... (from https://www.fns.usda.gov/nutrient-content-us-food-supply-190...) you can see saturated fat consumption going down as recommended, chicken consumption going up, even things like sugar has gone down recently. These obviously vary between country, but here in Finland people at large do seem to follow the guidelines especially considering school and work canteens, retirement homes and so on.
As they have held wildly different positions over time, they have surely been wrong and indoctrinating children on those wrong policies for decades. It's somehow assumed that they're either getting it right this time (if you voted for this group) or they'll get it right next time (if you're voting for the next group).
