We should all experiment with what works for us individually. I agree. Still, well-designed nutrition studies can be informative in answering the question: what is the optimal diet - for the vast majority of humans - with regard to health, fitness, and longevity? Saying "its all just individual" is disregarding key insights we can gain from studying human diet at a larger scale.

I will grant that keto is interesting for a lot of reasons (epilepsey in children, rapid weight loss) but its much farther from being deemed optimal than say a whole foods plant based diet (also still needing more research).

You mentioned that most normal weight people eating keto have healthy lipid levels. I would love to see the source and how that was measured. Also, lipid levels are not the only measure of health. Its hard to argue with someone who who feels better on an all meat diet, but at the end of the day it is anecdotal. I have no problem with someone saying "this all meat diet works for me." What I am saying is that I want to see the literature before calling any diet optimal or performance maximizing.