CICO is the explanation, not the cause. If you want to state, as above, that “calories in” (necessarily) equals “calories out,” then you are simply wrong. Likewise, people assuming that merely reducing the “in,” (without considering the “out”), will work well, long-term, for all who desire to lose weight, are incorrect.
I they were not considering “calories out,” or conjuring up an imaginary equals sign like somebody around here wants to do, then yes, they were wrong. You don’t think they were wrong? You don’t think they had a very low level of success?
I’d say a great many did not understand the implications of insulin, to start with. It is still this way for a lot of people. So yes - they didn’t really understand what they were doing. Yes, they did not “eat less enough,” i.e. they did not keep the “out” below the “in.” Once again, you can only be correct by considering both the in and the out. That human beings may go wrong there is just a fact, it’s not somehow “the fault” of CICO.
You can see that it’s really not very complicated, as in the Dr. Fung video. If we do not insist on neglecting the “calories out” part or conjuring up imaginary equals signs, then much of the battle is won. If they failed at weight loss, they failed at weight loss. This is a fact for many of us, me included. This was not because of some fanciful error in CICO.