In the absence of carbohydrates they are insulin sensitive, but I said physiologically insulin resistant, meaning they likely won’t pass a glucose tolerance test. I’d argue that it’s better to be insulin sensitive at all times and not just when eating certain foods.

On the “correct amount of hormones” many men doing a carnivore diet experience a decline in testosterone levels and some even have worse sleep (too much cortisol?). Many try to explain it away, but that has the same vibes as vegans telling ex-vegans that they didn’t do it right.  

Humans are unquestionably omnivores, and many of us are quite resilient and can thrive on many different diets. Some are less resilient and have to stick to only eating meat, but to say humans didn’t eat fruits and other carbohydrate containing foods, specially those living close to the equator, is just false.      

Insulin spikes are not inherently dangerous. As long as one is insulin sensitive they can be beneficial for nutrient delivery, and insulin itself is anabolic (muscle growth) which is beneficial for obvious reasons.