The truth is that human societies need some form of connection, through a grand narrative, to function in groups of any significant scale.

Sure, I don't know why you need a god for that.

The grand narrative of Christianity produced a civilization that I like to live in and don't want to see disappear. There is no other religious tradition that I would want to live under.

No issues there. I think we could be better, we just didn't actually try. Living under Communism's grand narrative is obviously worse than living under Christendom's narrative.