The role of insulin in every human is critical and works in conjunction with many other hormones. I am no biologist but my understanding is that when you eat carbs, an insulin response is required to process them. That insulin response may be a small one or a ginormous one depending on what's been eaten, and dependent on how your body is working no matter the type, the body will struggle to utilise that insulin properly or be unable to because of a lack of it. Even when injecting it, it still depends on interaction with your other hormones which may be working perfectly or may not.
I think you are saying that insulin and its role is almost casually tossed aside (especially in type 2 conversations) and its function across all diabetics is treated almost as an aside. I believe it should be right up there as a crucial factor in what diabetes is about and its causes, instead of this 'you eat too much rubbish and don't follow a healthy lifestyle' claptrap. I am not saying following a healthy lifestyle doesn't matter, of course it does especially when you have a health condition but I for one, am sick of this attitude of 'Your fault'.