religion is not there because it is useful, it is there because it is either the truth or a scam.
Atheist moral system below:
therefore
and
In fact "you" is a convenient abstraction for a colony of cells.
So what are you supposed to do? keep being what is defined as the thing that keeps being.
That's what you do, when you do good, and when you do bad. Good is defined what helps life in a long term/great number of brothers, bad is absolutely not the opposite of good, it is merely helping life in short term/egocentric perspective. That is, getting unfair advantage over others. Clearly understood by the biblical authors, the goat herders who define evil as obscurity, captivity, clearly misunderstood by a lot of other religions and Christian gnosticism.
So, believer can follow the word and example of Jesus, atheist can ask himself "am I helping myself and humanity in the longest term?" and act accordingly.
Also, there is one little thing, the abstraction called MEANING. When you do good or bad, the meaning of what you do is eternal. Eternal does not mean for a long time, it means beyond time. There is no arrow of time in meaning. All you need for meaning to keep existing is an observer. You are an observer. And for what concerns you, the universe begins and ends with you. And your actions have a meaning that lasts as long as the universe. If there is a god, what changes? The transcendent god is the observer, if he is just he compensates for the inherent injustice of the world. In his domain, time does not obviously exist (unless you believe in a religion where the superior arrow of time binds god, which makes you incredibly unatheist), so the judgment is eternal. Luke 16 talks about damnation after death, but the final judgment, the lake of fire, a new heaven and a new earth and, most of all, the new relation between god and creature are not compatible with eternity=infinite amount of time definition.
I only scratched the surface, my suggestion is to start thinking for yourself instead of following shit tier philosophers of today. If anything look up stuff written before the industrial revolution. People had clearer minds.