I do think there needs to be more science involved (and not necessarily Big Pharma inventing diet pills). The negative effect of yo-yo dieting is becoming more known these days as the body's response to the "famine" effect.
There could be genetic causes - there's one bit of studying I did around this subject, which in part focussed on the slave trade where the people who survived being transported across the Atlantic despite getting little food, water, and salt had very efficient systems and may have bequeathed that to their descendants who now live in a society which invented burgers'n'fries with their high fat and salt content.
There's also epigenetics as in the Dutch Hunger Winter where the effect was most noticeable in those who were foetuses at the time, and subsequently in the next generation.
Anecdotally, there's a family I know fairly well, where the females are all large. But one controlled her weight via a weight-loss organisation but never looked healthy. Her face was gaunt, and she didn't seem to have much flesh on her bones, but she was apparently at her ideal weight for her height. But she never looked slim, because she had wide shoulders and hips.
It's a bit like the current focus on BMI, especially the programme introduced for children, which causes all manner of problems because there seems to be little differentiation between "big" and "fat". I've often wondered if the historical picture of blacksmiths/farriers as being big and burly people was more related to their genetic capacity to maximise their calorie intake as opposed to building up muscle as a result of the job they were apprenticed to.
Obviously, all the above is fairly simplistic, but I think there needs to be a better understanding as to why some people end up overweight. Some of it could be genetics, some of it could be familial (fat children tend to be fat adults), some of it could be comfort eating/drinking, some of it could be not understanding how many calories they're consuming.
Is all that a means of providing an excuse? Not totally, because some people really don't know why they're overweight and, for some, the mantra of "eat less, exercise more" would give them the "how" but not the "why".