You're absolutely right that losing weight has a lot to do with psychology, and that the execution of it depends on finding a method, a diet tailored to the individual's needs, to succeed.

But that diet will only result in weight loss if there is a caloric deficit, completely independent of insulin spikes. Now, the trick to achieving and maintaining that caloric deficit over a period of time is an effort that is psychologically demanding, absolutely. But the weight loss itself is pure thermodynamics.

If your interest lies in designing diets or meal plans that help people achieve their weight loss goals, your focus should rightly be the psychological aspect of it. That's the battle. But at the end of the day, a caloric deficit is necessary, whether you choose to ignore that or not.

IMHO, diet and nutrition is confusing as hell to the average person, and hiding the necessity of a caloric deficit and instead talking about "good" and "bad" foods or macronutrients, is a poor approach in the long run. But that's just my opinion. The necessity of a caloric deficit is not opinion though, it's cold hard scientifically proven fact.