I think it makes sense to use the nova classification as a guideline. It helps but not all upf are equally bad. It depends on the ingredients

I think food that needs to add Flavor, Color, Texture because it has lost it on the way during "processing" is maybe not worth eating anymore. In a purely nutritional sense.

Colors, Flavors, Emulsifiers. But more than 50% of the UPF products contain added #sugar. If you add #glucose and all the dextroses we come to nearly 100%. Processing doesn't make food bad. Ingredients do.