Your local authority provides free poop-bags, Wow!
There is no Camino Authority (well except the Cathedral in SdC and they definitely don't do trail-side hygiene). Most municipal authorities in Spain cannot afford to provide public lavatories let alone free poo-bags. A Pueblo with a population of 50 doesn't scoop in much of a tax revenue. The taxes paid by the local Albergue don't go far. Bars and such along the caminos provide the usual facilities but reasonably expect that you'll at least buy a coffee or leave some cents on the bar and the rest of the toilet roll where you found it.
The only viable perhaps is if, perhaps, pilgrims of good heart do what they can to make up for those others who will discard without regard. Take a trash-bag with you, pick up what you can, take it to the nearest village dumpster. Walk on with a lighter heart. I'm not advocating that anyone try to deal with pooped paper or sanitary detritus. Even the Ditch Pigs struggle with that challenge; ( rubber gloves, salad tongs and a balsa-descarga help) but do what you can, do it when you can. No pride, no guilt, no rage.