I buy on sale, eat no meat and little dairy, buy in bulk, shop sales, cook mostly from scratch, bulk cook/bake and freeze serving portions. Little gets wasted.
As for protein for seniors, I stopped eating meat and dairy almost 10 years and am nowhere near protein deficient. Beans, nuts, oats, whole grains, tofu, potatoes, peanut butter, fruits and vegetables all contain protein.
Giant herbivores like giraffes, elephants, hippos, etc., all manage to build plenty of muscle without eating meat or dairy, despite the livestock industry's insistence that humans need to consume animal products at virtually every meal.