The purpose of black box perspective is to not worry about the "so much more going on". Regardless of what happens in the box the rules of energy must stay put. As for the human body, the science there is young, it's extremely complex, there's a lot of misinformation, a lot of it was grabbed by governments ("don't eat fat!") to ill effect. Let's not. Just take it easy with the portions.

Metabolism shifts are not that large. If you are following CICO, you're counting calories, and that is already an error prone process. There's not a big difference between "my metabolism shifted because of this odd food", "I drank some alcohol", and "I miscounted how much beans I actually had". It's fine, if you have a good enough weekly target and you stick to it, you will have a baseline. If you are not losing weight, reduce the target.

It will work. If you are saying it won't I want to see a straight up study that says it put 500 men on a 1500 cal/day diet and they didn't lose weight.

Note that I am only talking about the physical angle, not the sociological one. "Juice is not healthy" is, to me, a non-sociological claim, but a scientific one, and I would prefer that "x is unhealthy" means "x is mildly poisonous", not "x is calorie-dense", because there's nothing actually wrong with calorie-density.