It is way more complicated than that. The body autonomously regulates the amount of calories that you eat. For example when you exercise more studies show people will eat almost exactly an extra amount of food equalent to the calories exercised.

The average person gains an extra 1 to 2 pounds a year. It takes 6,000 calories to gains 2 pounds. This is about ~16.5 calories a day. About a fifth of a slice of bread.

This is an imbalance of energy, on a 2000 calorie diet, of less than 1%.

Be wary anytime someone mentions "scientists" in their argument. More than likely OP has no source. Nevertheless, I get his point. Basically, calorie-in/out is still very much used but it doesn't tell the full story. At the end of the day you will gain weight if you eat too many Calories, but eating an apple will make you feel fuller than a chocolate bar, etc. Scientists dont even have a stake in this really it's more like nutritionists, and the jury is out as to whether we can call them scientists.