> Religion probably worked well and bonding communities back when communities were small and homogeneous and had little contact with the outside world.

Religion has been more impactful in spreading knowledge and connecting cultures around the world than the printing press, radio and the internet combined. Religion for a long time was the only contact with the outside world. Christianity today is more or less the culture and knowledge from thousands of years and countless different tribes and cultures, fused into one piece. Spread worldwide by preaching, manuscripts, monks, monasteries and by the sword. Compared to most ideologies that only spread by the sword, ancient and modern.

The default human condition is to spread by breeding among your own people, and exterminate other people. Sometimes just the men and the boy children, to breed with the women. Sometimes by exterminating everybody and even eating them. Cannibalism and human sacrifice was the default human condition for tens of thousands of years, or maybe even for millions of years, before the light came to man.

Thinking that religion is only war and oppression is like thinking math is only for calculating artillery. It's a limited perspective.