“What is Religion good for?” is an important question because it’s entirely the wrong question.
The word “religion” stems from a Latin word meaning “binding”, and in its most narrow sense refers to those practices and actions we are “bound” to undertake in service and worship of the Divine. In its broader sense, it also refers to what devotees of that religion believe about the Divine. We often take this latter sense as the typical sense because Christianity emphasizes orthodoxy, literally, right speech, right thinking about God; but most religions historically have been about orthopraxy, right practice. For the Romans, rulers of the known world in Christ’s day, religion was all about orthopraxy—it was about offering the proper sacrifices to the proper gods at the proper time in the proper way, and they’d go to great lengths to see that this was done. If any slight mistake was made in a ritual, it had to be repeated from the beginning as many times as it took to get it right.
This led to the first clash between the early Christians and the Roman Empire. Augustus was given divine honors in various places in the empire during his life, and in Rome itself after his death; later emperors were treated similarly. Eventually it was required to offer a pinch of incense to the Emperor; it was a mark of good citizenship. Most Romans offered it willingly enough; Christians wouldn’t, because whatever else he was, the emperor certainly wasn’t Divine, and that mattered.
The Hebrews had always insisted that the God of Abraham, Isaac, and Jacob is One, and sovereign over all of the gods of the nations; but the Hebrews never really went in for theology in the modern sense. Like most other religions, the Hebrew religion was—mostly, not entirely—one of orthopraxy, not orthodoxy. But it was vital that you offered your sacrifices to the God of Abraham, because only the God of Abraham was truly God, the great I AM.
And that’s why the Christians wouldn’t offer the pinch of incense to the emperor: because it matters who you’re worshipping. God Almighty is worthy of worship. The emperor isn’t.
But this only matters if God Almighty actually exists, and if God Almighty cares. And so theology was born: the early Christians wanted to understand their God as best they could, so as to worship and love and follow him properly, and not fall into error about Him.
Which brings me to my point. It doesn’t matter a bit whether religion (in the broader sense) is good for anything if it isn’t true. If the God of Abraham, Isaac, and Jacob doesn’t exist, if Christ did not rise from the dead, then Christianity is a lie and a sham and unworthy of practice, and ought to be shunned by all good men. Any good that it does is in spite of itself.
And if Christianity is true, then it is the case that we have a God who deserves our worship, and who has the right to specify how He should be worshipped and how we, His creatures, should live. And in that case it is our part to submit and do His will, and to rejoice that God is a God of love and mercy.