Avoiding fads, eating cults and quick fixes is spot on. The right ballpark isn't rocket science, but most people simply opt for quick fixes because they think it'll allow them a way around what they consider the grind and some basic discipline.
I think it's slightly more complicated than that. In a world of noise, stress and poverty for a lot of people, there is no time to think before you do and no money to have a choice (bad food is cheap and fast!) so habit sets in. It's a form of poorly contrived efficiency. And then it catches up on you. I've been there. It's easy to point fingers at the food pushers, but there is only supply because there is demand when there shouldn't be.
If you look at the average high street here, it has descended into rows of fast food outlets. And this is because people have hauled their ass home finally at 8pm barely able to stay alive so they can sit in their box room until they have to get up at 6am the next day to go and sit in an office miles away purely sited for corporate status. Their only awake and "corporeal" time is during the commute and that's mostly standing up. That kebab shop looks pretty good then because the mind desires something to provide gratification in an otherwise empty life and instinctively we go for carbs as we've not evolved much past our stoneage scavenger bodies. Been there too
I'm not there now. I don't commute. I don't have that ball and chain. I can run a good 5 miles. i can climb 1000ft easily. But it took for me to throw my entire life away and take a lot of risks to get there. And most people are afraid of that. I was and I'm not sure I recommend being left with £12 to your name on at least 2 occasions
Collectively we created a monster as a species and now it's eating us.
Edit: I'd argue most of us are victims of circumstance and necessity. Bring on Star Trek replicators. That would end everything overnight.