(I have no expertise in biology, spitballing): One other benefit of sexual reproduction is that you could get a stable equilibrium with diverse phenotypes. Imagine that giraffes eat from Acacia trees and Baobab shrubs. You need to be tall to reach the Acacia trees and short to reach the Baobab bushes. An asexual organism would have to split into two niches, one that grows tall to each Acacia and one that is short to eat Baobab (maybe even two different species). A sexual organism could have a gene with X and Y types where if your alleles match (XX or YY) you're tall, and otherwise short. If the less common of {tall,short} is more fit, then you'll have an equilibrium where X and Y alleles are equally common in the population. You have to have a story for why this is better than two separate species, one to eat Baobab and one to eat Acacia. Maybe cooperation is easier among organisms that can till reproduce sexually instead of being symbiotic but separate species? Maybe it's as simple as staying the a unified species leading to greater genetic diversity.
(I have no expertise in biology, spitballing): One other benefit of sexual reproduction is that you could get a stable equilibrium with diverse phenotypes. Imagine that giraffes eat from Acacia trees and Baobab shrubs. You need to be tall to reach the Acacia trees and short to reach the Baobab bushes. An asexual organism would have to split into two niches, one that grows tall to each Acacia and one that is short to eat Baobab (maybe even two different species). A sexual organism could have a gene with X and Y types where if your alleles match (XX or YY) you're tall, and otherwise short. If the less common of {tall,short} is more fit, then you'll have an equilibrium where X and Y alleles are equally common in the population. You have to have a story for why this is better than two separate species, one to eat Baobab and one to eat Acacia. Maybe cooperation is easier among organisms that can till reproduce sexually instead of being symbiotic but separate species? Maybe it's as simple as staying the a unified species leading to greater genetic diversity.