How does "nothing matters" follow from "things are what they are"? If we ascribe the ability to create "meaning" to the hypothetical heavenly intelligence, why deny it to our own (factual) intelligence?
And religious morality, deep down, is relativist, because it is based on authority: basically, there's no right or wrong, there's only what He says (in the interpretation of your friendly local priest, imam, shaman, or comrade commissar, naturally).
Meanwhile, the Golden Rule is shared, in pretty much the same form, by religious, quasi-religious (like abovementioned Taoists or Confucians) and non-religious people, throughout millennia and across continents. You don't need to believe in the Imaginary Friend, to be moral.
(Now, I will be the first to say that people losing their faith as a result of some political upheaval or a propaganda effort tend to get stranded in moral vacuum, and that may lead to terrible things. But this is very different from every individual human mind evolving toward atheism).