I can't speak for the OP but it is well-established that there are significant genetic adaptations to the amount of meat in the diet, or a loss of genetic adaptation for metabolizing some plant staples. This is no different than the genetics that cause significant variation in the ability to metabolize legumes, lactose, alcohol, etc. Local optimizations.

There are ethnic populations that have reduced capacity to efficiently metabolize some plant-based diets due to thousands of years of selection pressure (or lack thereof). A diverse plant-based diet won't kill them, they simply lack the enzymes to have a good experience with it because for thousands of years they had little use for those genes.

It is a relatively small population globally, as it tends to coincide with regions that weren't conducive to supporting large populations thousands of years ago. The current distribution has significant overlap with the developed world though.

I have to imagine that someone with meat-adapted genetics is going to suffer quality of life issues on a purely plant-based diet. Everyone has a set of foods like that.