If you're going to complain about misunderstandings among laypeople, let's start with the proper name for the unit used pretty much everywhere: you're talking about kilocalories when you talk to a layperson in the US about the "calorie".
Second, even if in a typical case we could perfectly balance energy intake to activities, it's been shown that many bodies are atypical. We are not feeding spherical cows of uniform density in a vacuum. These are people with more or less muscle mass, different things going on in their endocrine systems, different overall body mass, different drug intakes, different vitamin and protein levels and sources, and different genetics.
The real-world test for a dietary plan is whether it helps you maintain your health and desired weight. There is enough research to recommend some alternatives as definitely better than others, but there's been no definitive perfect diet. Ultimately the perfect diet is one that allows you to be both healthy and satisfied, and that it can't do on its own. The dietary plan can contribute, but it also takes other lifestyle factors.