Carbs, not because they're inherently wrong, but rather it is super easy to eat an extra 200+ calories when eating them. All it takes to gain weight is 200+ calories than your maintenance. That can be an extra handful of chips or another slice or two of bread.

I think where mainstream nutritional science is going is understanding that people's 'maintenance calories' is insanely hard to calculate for people outside the average. For instance hormones playing a much bigger role, where your calorie range is off from what models will say, so unless you know how to safely find that maintenance and treat your diet like science to find it you're going to constantly be over/under weight.

This science is showing more the combination of extremely fatty and carby food at once has a distinct reaction in our body. Where yes it is 'calories in calories out' but that doesn't mean that our bodies don't have their own agenda in terms of using the calories in for fat stores vs energy for activities. Almost like moving your maintenance calories to a lower number when you're eating mostly heavy fats and heavy carbs while being extremely stressed out has a ton of hormones that screams to your body save as much of this as possible.

If your diet is 30-40% protein and not having refined sugars, you'll feel fuller and won't feel the need for more carbs besides indulgence/treat. You don't need to do this to lose or maintain weight, but look at 300 calories of beef or chicken breast vs 300 calories of bread.

The only problem is cost, if you're not careful you go from a daily cost of 3-5$ in groceries to 10-15$ to eat enough protein. However, means doing bare minimum exercise daily with this diet going over in calories will build muscle, and going under (not going past 400-500 deficit) you can lose fat and gain muscle.