This is the argument i'm seeing here: "The balls to refuse other women's advances and stay in a committed relationship" is more alpha than "Indulging their base desires and engaging in free sex".
Reito's character is consistent, it has not changed, Doi's character has undergone quite a few changes, it has developed, and Kyouji has adapted to the new world like a fish to water.
Reito is not a relatable character because most of us haven't been in a truly committed relationship, and Doi isn't relatable because most of us weren't socially crippled by being beaten and bullied to the point of mental trauma in high school.
I believe most of us would have chosen to indulge for a while as Kyouji did, and eventually built a close relationship with several women we had impregnated creating a family(harem) while "donating" sperm on the side until the day we die(the UN killed the rest of us).
I'm not a manga protagonist that would push a boulder up a mountain trying to save a world that frankly doesn't seem to deserve it, most of the men are dead, they aren't coming back, let the psycho lesbian feminazis have their female-only "utopia" so we can enjoy watching it crash and burn in spectacular fashion, I'll be laughing my ass off from whatever afterlife will have me.