Here's the received wisdom:
Humans have long suffered from various emotional and psychological needs and fears. So, seeing as the real world is harsh, indifferent, and unresponsive to these needs, humans in every age have fabricated gods and godlets to meet every little need. Finally, however, mankind has been freed from this craven superstitiousness and can now walk on two feet into the horizon of pure reason and exact science. There is no God; He's just been made up by precocious anthropoids in an existential bind. This is certainly the most basic objection to theism: "You know that's true, it's made up. So believing in X, Y, and Z is not only pathetic but also immoral. Humans should only believe what is objectively true and should proportion their adherence to a concept or claim based on the evidence for it. God is just a crutch."
Unfortunately, however, the psychological needs are still with us. We still limp. We simply can't function without meaning and purpose, value, hope, and unhinged love. So the new wisdom's solution is to beat the religious at their own game. Seeing as, on the one hand, there is no Meaning in the cosmos, since there is no "Meaner" in whose divine eyes anything and everything has meaning, and seeing as, on the other hand, humans are driven by their irrational evolutionary heritage to seek what is called "meaning," the best solution is just to make Meaning up as we go. If there is no meaning in the world to be discovered and cherished, then we had better just make it up ourselves.
At this point, however, the jig is up, rationally speaking. For it is the same people who in one breath castigate Christian believers for "just making up their god talk," for cherishing a make-believe world, who now, in the next breath, praise nonbelievers for making up the meaning in their lives, for cherishing a make-believe schema of value and meaning that has no more "objective" place in the world than, arguendo, God Himself. The atheist way, thus, enjoins men and women explicitly to believe in a fabricated Meaning and to proportion their evidence precisely in inverse proportion to the evidence for cosmic Meaning, namely, the total lack thereof. Precisely because there is literally no evidence for a higher purpose or a grand meaning in our world, we have to believe we can forge it every step of the way, and that, in an explicitly anti-evidentialist manner.
I have written before about the failure of paganism -- which I dub "utilitarian piety" -- to meet the true needs of human nature, even as it is mounted on precisely the premise that meeting those needs is the essence of religion.