He may develop sepsis. Non-healing wounds lead to amputation, which threatens death at various stages. Even increasing the likelihood of snagging when walking. Deep vein thrombosis may develop, and a broken blood clot will block the lung or fly towards the heart, for example. Gangrene may develop, often dry, which also leads to amputation or immediately to death. Well, with any surgical intervention, you can kill yourself in the process, including from intolerance to what they were given anesthesia, or from the concomitant load on the heart, which is very dangerous in old age. And diabetes itself remains.
One old man lost a large rusty nail and walked with it in his foot for a week (his leg was eventually amputated).
The patient's legs will begin to form trophic ulcers, they will grow in size until they merge into one continuous decaying wound. The person will die from sepsis.