Your original argument was "there is a small talent pool for MMA compared to other sports." My counter on why that is incorrect is "a larger number of people can participate in MMA compared to other sports (which require above average size) due to weight classes." Not for nothing, the largest weight classes are LW and WW, which correspond roughly with the average weight of Western men when adjusting for the weight cut.
I have no idea what your reply has to do with that.
Flyweight is poor as a division because there indeed not many men who can meet that weight requirement, but back to my earlier point, Mighty Mouse ain't ever gonna be a NFL running back. Heavyweight is poor because the big men prefer to compete in sports that are much more lucrative (and also require that aforementioned size).
TBI in the NFL has been known to the general public for nearly a decade now, and we've seen no decrease in the number of young men entering the NLF in that time or the foreseeable future. Note I said "general public." Players have known the sport takes a heavy toll on the brain for decades. I spoke with Gary Fencik a couple years ago, and I asked about TBI during his time in the NFL. He said something along the lines of "We all knew it was doing damage to our minds. It didn't change anything. We just wanted to play."