Evolution doesn’t really care about quality of life, so long as an organism still reproduces. If every organism in a species is in horrendous, absolutely unconscionable pain and suffering for their entire existence but always manages to successfully pass on their genes, then the species can absolutely be deemed “successful”. In a way, we have a symbiotic relationship with e.g. cows: even if we cause them mass suffering as individuals, as a species our relationship is mutually beneficial and that’s all evolution really cares about at the end of the day.