My main argument against doctors who just prescribe drugs for dietary/lifestyle 'diseases' is that - certainly there's a failure rate amongst those who try to control their diabetes, blood pressure, obesity with diet/lifestyle, but unless the patient is informed, they don't even get the chance to try it!
When I told the DN what I was going to do, she first said "nobody ever succeeds". Then when I was succeeding You won't keep it up".
Then when my HbA1C was below even pre-diabetic "none of our other patients would be able to do that".
To which my reply was - "well if you don't tell them that it's possible, how do you expect any of them to do it"! And of course, they don't!
You may wonder why almost all interaction has been with the DN rather than the GP specialising in diabetes. - Simple, they don't want to waste his time on those who are doing OK. It's the HbA1C results which determine if I see the GP or not, so I only saw him after the first and then the confirming HbA1C, never in the 4 yrs since then.