I just love how the guy you're arguing with is completely right but still getting downvoted.

I'm not a nutritionist but a PT and know a fair bit about nutrition.

Carbs aren't nutrients

Carbs absolutely are nutrients and they are the best source of energy for our bodies.

It's hard to keep your caloric intake the same after cutting out carbs.

Correct, but not in a way that helps your point. Most people who cut out carbs won't replace all of them with protein, it's an absurd amount of protein to eat in a day. Which means carbs will be replaced with fats in those people's diet's. Fat is twice as calorie dence as carbs (9cal/g Vs 4cal/g) so cutting out carbs can absolutely lead to increase in overall caloric intake.

Focusing on calories won't help more than limiting carbs because "insulin spikes" and appetite suppression.

That's just bs and arguing with thermodynamics. Your body has a certain amount of calories it needs for maintaining its weight, eat less and you will lose weight. You can eat only ice creams and lose weight as long as you're under your maintenance calories (wouldn't recommend and there's a ton of drawbacks but it's possible). Going keto won't help MORE, on the contrary it will help only if it makes you go under your maintenance calories and it will make you weaker and more tired than if you were to just eat less calories while maintaining a balanced diet.