The fact they’re not frozen isn’t what makes them not crispy; it’s the fact they don’t par fry them. Frozen fries are just par fried before freezing. If you fry them twice, you get the same texture. You can make McDonald’s style fries yourself at home from fresh potatoes by frying them twice, with a rest period in between. The only other thing that significantly alters the flavor is the kind of oil you fry them in.