The imbalance of fat to muscle leads to insulin resistance. Insulin resistance gets in the way of weight loss. After a long time of trying other means, I decided to directly tackle the insulin resistance problem. And it's been the only thing that's worked.
Sustaining that healthy diet is harder insulin resistance, agreed!
But you said you ate healthy for a decade. To me that's not eating obesity-maintenance level amounts of otherwise healthy foods, but rather eating healthy foods at a normal (say 2500 kcal daily) amount.
In other words, under your statement the behavioral impact of insulin resistance was already overcome, you were eating properly, and still didn't lose weight. And that's just not conform the science, which states that you lose weight even with high insulin resistance, as long as you're eating healthy (i.e. in a caloric deficit vis-a-vis obesity level maintenance).