There's still a massive difference between eating food that's digested over a long time and eating candy with the same calories. It impacts the whole process and how much people will realistically restrict themselves. There's issues with body image where people don't realise they're actually obese. There's comfort food related to life stress. And so many other issues. Sure, calorie restriction is an important piece of the puzzle, but saying the rest is a distraction is a really shallow understanding of the problem. It's like that "how to draw an owl" meme - true, but the instruction are so simple they're useless.