I did carnivore for a several months a few years back, and felt great. Shredded a ton of subcutaneous fat around my torso, and it resolved any GI issues I had (occasional bloating/constipation/gas) and my bowel movements were always quick and easy. Energy levels felt kinda similar to keto, stable and flat, but no dips or valleys. Mood was great and brain fog was eliminated. I really don't think this is merely the result of an "elimination" diet, but something else that really warrants more investigation. For instance, when you don't eat carbs your body doesn't need vitamin C because glycogen apparently increases your bodies needs for vitamin C by several magnitudes. I believe this is just the tip of the iceberg.
That said, I didn't stick with it mainly because it was boring as hell to eat the same shvt all the time. And as of now, I think fad/meme diets are kind of stupid, as are counting calories and macros, because it takes the focus off quality of ingredients and puts it on arbitrary things. For instance, people who insist on gluten-free diets end up eating tons of gluten free products that are processed and high in sugar, or vegans end up buying "vegan meat" which are all extremely processed frankstein products full of bullcrap that is terrible for you.
I think the key to eating well is to solely focus on eating high quality, whole foods, and paying attention to how your body feels after the foods make you feel. For instance, in my case most carbs make me feel like garbage, but I can eat a giant bowl of rice with protein and feel great afterwards. I can even eat pizzas that are made with fresh, unprocessed ingredients and feel fantastic after. Takes some trial and error to hone in your diet and find out how your body responds. I do not believe in the "one size fits all" diet advice that has certain axioms that must be followed and must be applied to everyone. Everyone has a different biochemistry and gut biome and some foods may be appropriate for one person, and not the other. Just listen to your body.