1.

If we're talking about this as a public health issue, then I agree with you. You can't really expect much of people as a herd or mass.

(Hell, look at the state of elections.)

If we're talking about this as individual, rational people, though, then it's different. You can absolutely maintain a reasonable weight if you just attend to it.

2.

There's actually some knowledge embedded in the "count to 1500", which, if you're not in the habit of thinking about, may be surprising. Specifically, the kcal amounts themselves.

Say you just go with the flow of society, and you eat "normally" without thinking about what you're doing:

You wake up, and you have something marketed as "a meal" for breakfast. A breakfast sandwich can easily be 550 kcal. If you add a venti latte to this, especially one with sugar, then you could easily add another 250 for that. Now you're at 800 kcal just for breakfast.

Then consider lunch. Even a "small" meal from a healthy salad place, like Sweetgreen (which is expensive), is going to be like 900 kcal. Say that's what you eat. Now you're at 1700 kcal.

The afternoon comes, and you have two chocolate-chip cookies. Two cookies isn't excessive, right? Just a little treat. But each one is probably 120 kcal. So that's 240 kcal. Now you're at 1940 kcal.

Finally you have dinner. Some microwaved thing, relatively small. It's probably like 600 kcal. So now we're at over 2,500 kcal for the day.

Everything you did in the course of that day was relatively normal. Probably only the venti latte at breakfast was obviously excessive. But now you're substantially over your calorie budget.

Now, 2,500 kcal is still salvageable. Every mile you walk on flat ground is about 100 kcal. If you live in the city, you could easily have walked a mile and a half during your commute to work, and another mile when you stepped out for lunch, and a mile and a half on your way back, giving you four miles. You're almost at breakeven. Just need a little more exercise, and you'll maintain your current weight.

(In the burbs, though, you probably drove to all these places and now it's on you to go to a gym, which is a pain in the butt.)

Anyway, my point is, if you weren't attending to all this, how would you know? You'd probably just be doing all these habits without thinking about them. Most parts of this routine seem pretty reasonable. But you'd still be getting fat. Because you're going with the flow instead of counting.

So, there's a little (easy) knowledge involved, but mostly it's not an issue of intellectual ability, it's a matter of attention.