Is it true that the conventional wisdom is that type-2 diabetes is not curable? I've never gotten that impression. Type-1 is not curable, at least unless we can figure out how to get the pancreas to begin producing it again in those individuals where it stops doing so. But type-2 is insulin resistance, and it's considered to be reversible with proper changes to diet, isn't it? My doctor recommended a low-carb diet (just one reason I like him) because I'm right on the edge of type-2 diabetes.
As for diet, I don't think there's one single perfect diet for humans. But if you listen to the various types of diets on offer, you can find some things that they agree on. Usually, there is an emphasis on natural over processed food and on avoiding or reducing foods with high sugar/salt content. Prepare and cook your own when you can, and use fresh ingredients whenever possible. Find a level of exercise and diet that keep you where you want to be, and stick with it. Avoid short-term fixes, which only last for that short-term and often leave you worse off afterwards.
As the saying goes, it isn't always easy, but it is quite simple.