I don't know how things are for anyone else, but it worked for me, shrug.
Attempts to loose weight by diet only all failed. To make it worst, there is also aspect of most common diet advice being plain wrong. It focuses on calories too much. It completely ignores what your body needs, so you end up in nutritional deficiency - this kind or that kind. And that will affect a lot and eventually you will stop diet and start to feel so much better and healthier after stopping it.
The calorie stuff is from both oxygen and deuterated water studies. You burn the same amount of calories and your system just shunts them around. The science on this is one of the few things in nutrition that is quite solid.
This has the effect, for example, that if you exercise a lot, this actually suppresses your immune system making you more likely to get sick.
While I do agree with you that sustained, high level activity requires and burns more calories, I think that the advice coming out of there, exercise is less efficient than diet for weight loss, is going to absolutely be true for the majority of gym goers who quite frankly are phoning it in whenever they work out.
Like, for example, an olympic swimmer may eat 5000-10,000 calories in a day, but they are spending around 4-6 hours a day in a cold pool training at a world class level (body needs to keep warm somehow regardless of effort.) But a normal person may only swim for 20 minutes at a much gentler pace. This person should still be eating in line with calorie guidelines and macros for age/sex.
The reality is that diet needs to be flexible based on results. Not losing weight? Eat fewer carbs or calories. Feeling tired and worn out? Eat more or exercise less based on your physique and goals.