If you are an agnostic then what do you mean by "morality" other than what YOU think people are better off with than without? And what standard would make your morality better than another agnostic's totally different conception of morality? In terms of civilization, the most successful civilization the world, Rome, was completely immoral from a contemporary point of view. People butchered and fed alive to animals for entertainment and sport. Armies pillaged cities and killed every inhabitant or sold them into slavery. The army routinely killed or whipped their own soldiers to maintain disipline. The Romans considered this completely "moral" and their civilization lasted almost a thousand years.
The same as you, codes of allowed or favored behavior.
... other than what YOU think people are better off with than without?
It's not really what I think, but what people generally think that's important. Don't you agree that people would agree they are better off being able to trust other people not to steal from them or kill them?
And what standard would make your morality better than another agnostic's totally different conception of morality?
Based on their different outcomes of course. It's an empirical question. But I admit it may be hard to infer or discern the difference enough to say a particular one is better than another particular one. That said, one ought to always be looking for improvements.
In terms of civilization, the most successful civilization the world, Rome, was completely immoral from a contemporary point of view.
No, they were not "completely immoral" even from a modern viewpoint. Nor would I consider it the most successful civilization in the world so far, the United Stated is and before us it was the Brits.