I think the major problem with CICO is that advocates for it present it as if it is a diet when it's actually just an explanation for why diets work (or fail).

I've seen a lot of threads with people asking for advice on losing weight and inevitably someone chimes in with "Calories in, calories out." Great, but that doesn't provide any strategy or guidelines for actually losing weight. Calorie counting and tracking is a strategy (and so are many other things, like intermittent fasting, the potato diet, etc. As long as at the end of the day you are at a calorie deficit).

Additionally CICO ignores the reasons why people overeat in the first place. There are a lot of physiological and psychological reasons for that. Maybe someone is overweight because they eat to cope with trauma. Maybe they have a hormonal imbalance that doesn't properly regulate how full they feel. Dealing with those underlying issues is often more beneficial in the long run.