I don't know if it's a solved problem. It's very hard to get people to fast. It's even harder to get people to maintain a healthy lifestyle and body weight after going into remission.
I wouldn't be able to do my job if I did an 850kcal fast for 3 months.
Doing intermittent fasting isn't even that taxing once you adjust. I have been doing it for around 4 years and I work as a developer. My most productive hours are still in the morning, and I don't even eat until noon-1pm on most days.
But to your point, yes, a drastic implementation of a clinical approach can be impractical. Fortunately there're a lot of ways to fix type 2 with diet which aren't as taxing.
So the problem is solved. It's just that most people would rather take insulin than change their diet.
We found a similar problem with smoking. Numbers of smokers have reduced with public education plans and limitations on marketing. Perhaps there are similar things that can be done to help reduce the number of people suffering obesity related illness. Perhaps it's something that will have a net positive impact on society as a whole?
There is of course a balance interfering with individual dietary choices is a slippery slop, freedom must be preserved at all cost.