Atheism is a belief that there is no God. Anything else is just cosmetics.
Most Atheists I have come across (myself not included) don't identify with that statement so your definition doesn't do a good job of differentiation.
As a negative belief, it takes away from the individual rather than offering anything to the community.
It contributes a critical thought process to the society. How to distinguish between reality, illusion, delusion, and hallucination for example.
All religions have established societies and social orders, while atheists even today are consistently obsessed with personal rights, taxes and responsibilities.
Atheism isn't intended to do establish societies and social orders. Religion should not be establishing societies consequently.
They do not, as athiests, have anything to offer in terms of ethics or social order to the community. But they play a valuable role as whingers, though one can have too much of a good thing.
They offer quick identification of when a religion is overstepping its bounds . Again, atheism isn't meant to do any of those things you listed.
For any person to travel anywhere in the world and meet a Christian, a Muslim or a Parsi, is to meet the member of a group. To meet an atheist, is to meet an unknown.
I have a sneaky suspicion that the unknown consists of many secular humanists.