It is a myth born of the Renaissance that society is getting better, that we are making strides, that human rights are improving. Society is NOT getting any better. People still kill people, despite the death penalty. People still commit crimes. I would bet my right arm that there is an Athiest somewhere that has committed a murder. People still die, wars still are fought, and people continue to hate others for stupid reasons or even no reason at all. There are still hate crimes: crimes based on race, religion, and sexual orientation. People still get discriminated against, whether it be due to race, religion, sexual orientation, or gender.
Christianity has changed quite a lot, believe it or not! They adopted Christmas trees, eggs and rabbits from Germanic Paganism. Every time that they take over a religion, they add something to their melting pot that is Christianity, just to ease the conversion. For instance, when Christianity took over the Germanic peoples, they could not stop them from celebrating their seasonal festivals - so they just adopted them. Even changing the season of Christs' birth!
To you it may seem that religions change little, but they change all the time, and Christianity is a big culprit. Religions survive as long as they are useful. I am enjoying a revival of my native religion, Asatru - people of Northern European descent want purpose and meaning - and for some, I suspect a lot, that Christianity doesn't give them what they need spiritually.
I doubt that the gay issue will break religious intolerance. The way that the fundamentalists read scripture, homosexuality will always be an abomination; a sin against god.
I like your question though. Food for thought!