I have read this answer to a different question which discusses a theory of the cause of type 2 Diabetes. It describes insulin resistance leading to a runaway positive feedback loop. The answer also suggests family or lifestyle factors being the cause of the insulin resistance.
I’m wondering if the current evidence we have suggests that any human could get Type 2 diabetes, or if it is possible that someone who is unambiguously human, (not a created via injecting non-human genetic material into a human egg for example,) who cannot get Type 2 Diabetes under any environment. For the purposes of a clean way to tell if something counts as Type 2 Diabetes, I'll specify that anything with the same underlying mechanism as something that is unambiguously Type 2 Diabetes counts as the same disease.
I suppose that I could formulate at least two forms of this question, by varying what counts as "any environment". The first form would include injecting fat into the person's liver. A second form would exclude all coerecion or direct modification of the person's body.
If we knew that someone who could not get Type 2 Diabetes existed, then I would argue that it would make sense to call Type 2 Diabetes a purely genetic disorder, even if the population with the disorder included every human except a single individual. Does that method of classification make sense?