Adherence to avoiding UPFs, by the current Nova classification, would lead to most people having to radically change their diets, assuming you actually follow the Nova classification of UPFs to a tee. And assuming they're already reasonably healthy, there would be no meaningful health benefits I suspect.
Potentially there could no noticable health improvements but potentially far less health degradation over time when you think about things like risk of type-2 diabetes with high sugar and high-UPF diets.
But it's true that we mustn't focus only on UPFs but it is looking more and more like a significant factor (even if the definitions could be improved).
Again, I’m not saying “all UPFs are safe/healthy”. I’m saying the definition is worthless when you include potato chips and protein bars in the same category.