Indeed. Keto doesn’t work for everyone. (Some people can’t even try it, actually, maybe they don’t necessarily count though.)
Even on this forum, it’s shown that it’s the case. Some people feel way better when eating certain plants.
And some people are thriving on high-carb, for example my SO.
And I think human history quite thoroughly proved that humans handle carbs… Carbs kept most of humans from dying due to starvation, after all. It’s not the most important macronutrient (as it’s not even essential) but for energy, it works. Especially if one is used to it. (Even though I handle carbs the best after carnivore times. They just add up in my case. Still, I handled them way better before I went low-carb. But now my body saw a way better option and it complains if I am stupid )
And let’s not forget, not only super unhealthy carby diets and keto/carnivore exist. A health-conscious high-carb diet may be the best diet for someone who doesn’t seem to handle low-carb (as my SO. he is starving, overeating and gets unwell on low-carb. ONE very specific low-carb meal was the most he could do. but table sugar? highly processed items? well if the best sausages are highly processed than yes but otherwise… and he eats like 1 per month anyway, I am the “big” sausage eater. my body approves).