Why is the parent rated insightful? It's simply wrong. Worse, it tells people they have no control over themselves thus implying they should give up trying to lose weight rather than find good information.
Calories in, calories out (CICO) 'works'. It's a law of physics. Matter/energy doesn't randomly appear or disappear. The problem is people have very little control over CO. You lose weight by spending time in a ketogenic state (when your body is pulling energy from your fat stores rather than the glucose from your recent meals). The two easiest ways to do that are either a long term ketogenic diet or water-only fasting (stupidly named as you're fasting from food, not water). You can workout to get into a ketogenic state faster, but if that workout burns above around 200 cal, your body will dynamically down regulate it's systems to spend 200 cal less that day. You have an energy set point it tries to reach each day with a wiggle room of roughly 200 cal above and below that. There are tons of studies and a few books about this.
The above is the physics of your metabolism. There's also nutritional cravings. If you're low on a nutrient your body will crave foods that taste/smell like they have it even if you've eaten enough energy. Artificial/Natural flavorings trick your body into thinking a food has something it doesn't. You'll crave that food more and more as you try to extract a nutrient it doesn't have. That's the 2nd reason people can't stop themselves from overeating. (1st is insulin swings, 3rd is carb addiction / emotional eating). There's also a few things (PUFAs?) which mess up how your body uses energy as well as some hormonal problems, like a messed up thyroid, with cause weight control problems too.
Not taking into account the above items as well as social pressure means people will regain their lost weight. That's doesn't mean their weight loss failed, it means they got fat again. If you fall off a ladder and break your arm, you get that healed. If 2 years later you fall off again and break your arm again, that doesn't mean your 1st healing failed and your arm was broken the entire time. You broke it twice. You can get fat multiple times too. Our society has significant peer pressure towards eating and doing things that get you fat. Exercise is the least effective weight loss method due to how your metabolism works. Anyone talking about exercise for weight loss is someone worth ignoring.
You don't hear much about this because there's no money behind it. No one is advertising how to do weight loss properly because there's nothing to buy except some very cheap salts (you need to maintain your electrolytes if water fasting for over 2 days and a multivitamin if doing it for months. Longest zero-food fast was 2 years). But it's all there in the science and research if you look for it. Just because something isn't blasted into your face from the media doesn't mean it doesn't exist. If your only information for a topic comes from mass media, you are significantly misinformed about that topic.