People start a carnivore or ketogenic diet and say they feel bad....well YEAH! you have been running off of glucose for probably your entire life so your body may not be that efficient at running off fat for primary fuel. You are not going to feel great until your body has adjusted to the fuel switch and become better at utilizing fat for fuel.
Yeah I'm with you I totally get that. Like you, I've done keto for long periods of time and feel good. I actually like how I feel in ketosis. I also eat an ungodly amount of greens on keto diets along with fat from other sources like avocado, etc. etc. When I did carnivore I solely ate meat (I'm not sure if some add in other fats at all?). I just noticed a difference even starting to add in eggs, avocado, olive oil, and greens.