Yes, this is along the lines of my thinking. Nearly any "diet" you see here or elsewhere has limitations that make them less than optimal for ad infinitum (permanent lifestyle) change. Dietary variety could be limited, reducing overall nutrient intake and perhaps more importantly, the changes are not subtle enough compared to one's previous dietary habits and social/financial/physical environment that have been entrenched over many years. Asking someone to just jump right into a very low-carb diet or eat 10 servings of veggies per day very rarely lasts. The rule of behavior modification is that only small changes are incorporated long-term - and those are the ones that induce real bodily change.
Since the reality is that many people want a fast solution, however, I simply distinguish between "long haul diet habits" (better but slower) and "target date" types of diets. In a world of charismatic gurus and catchy diet books and systems, I hope this makes sense.