> It's easy to see the negatives really hard to see the positives but they will be huge, it's so ingrained it will have shaped everything. We will perhaps never know if it was a net gain or not.

Perhaps for you, but in any case, "religion" is not a single thing and not all religions are equal. Besides, every society has a religion. Every person has a faith. In the US, it is liberalism. In the Soviet Union, it was the Marxism/Leninism/whatever and the State. In medieval Europe, it was Catholicism. For Richard Dawkins, it is scientism.

And the only measure worth discussing is whether the religion in question is true. Your phrasing suggests you see it as some purely instrumental fiction. I reject that view because holding to a faith for its purported "benefits" is an act of bad faith. You believe things because you have reasons to believe they're true, not because you think they'll produce some desired result.