Certainly, atheism isn't a worldview so it shouldn’t be expected to come with a set of moral values. Atheism was originally defined by religions as that which is beyond the pale for denying the religion.

But we all face the atheist's choice to be good or to be bad, or the test of our willpower and of our faith in ourselves. That's the existential predicament. It's just that that plight bears down on atheists because they lack some of the core delusions that sustain religious people's preoccupations and prejudices. Religions don't rationally justify their values. They only tell stories to enable intellectually lazy folks to suspend their disbelief and to defer to a religious institution.

Atheists or secularists are indeed on their own, but so is everyone in reality, assuming there's no God or relevant supernatural dimension. We're all obliged to figure out how we should live. Again, that's the existential human predicament. Most people shirk that responsibility because they choose the easy way out. They're mentally "inauthentic" in Heidegger's sense. Or their morality is a form of slavery, as Nietzsche says.