I don't believe in reincarnation but let's entertain the idea of it. If you were reborn with no memories and knowledge of your past life, are you really the same person/soul since then?
If yes, why don't I know what I'm being punished for? What will keep me from repeating the same crime in the next life where I will supposedly be reborn as a Chad?
If no, why is the karma system (however it's called) punishing an innocent soul?
If this life is a punishment then it makes no sense since we don't know what we're being punished for. So what, I'll suffer in this life then be reborn as a Chad to be "evil" once again? Seems like an ineffective system.
Also, the issue of the population not being static is present.