The big issue with shoes and diabetes occurs if you have neuropathy in your feet–pain or most importantly numbness.
The reason is that when your feet are numb, it impacts on your immune system’s ability to fight infection. Partly it is because there will be vascular damage with numbness, but another reason many doctors even don’t know about is that it turns out that the nerves communicate via the Vagus nerve with the brain and this modulates the immune response. Dead nerves mean that the immune system doesn’t get the message “Invader, prepare to board!” So infections once they set in become extremely difficult to fight no matter how much antibiotic you pour in and this leads to gangrene and amputation.
So if you have neuropathy you must be obsessive about keeping your feet clean and away from anything that could damage them. If your feet are numb, you may also end up getting cuts etc and not notice. You are also at more risk for invasive fungi normal people can fight off.
So if you have any numbness or pain in your feet your shoes must 1) NOT cause blisters which can become infected, 2) cover and protect you from dirt. No sandals!
I don’t have diabetic neuropathy but I burst a disc years ago and spent about 6 weeks with a leg that was numb in the “knee sock” pattern. I ended up with an intense case of athletes foot fungus between my numb toes, which only went away when I recovered sensation. I’d never had atheletes foot before or after. If the numbness doesn’t resolve, that fungus can become limb threatening.
As a final word: YOU DON’T HAVE TO DEVELOP NEUROPATHY. Keep your blood sugars under 140 mg/dl as much as possible as that is the level where studies show neuropathy starts to develop and it might be worth trying benfotiamine, too as there’s some intriguing data suggesting it might prevent neuropathy.