The passing of monotheism is a confusing question for many believers. In fact, it is more than just a humanist critique of religion. It is a kind of epochal tide that, to a very long view, somehow conditions the histories of religions.
It can be useful to look at religion in terms of the eonic effect, itself a neutral repository of data sets and bibliographies: The eonic effect merely points to the Reformation and the rise of a new age of secularism (the latter itself a bit of a misnomer) associated with modernity.
To a longer view we can see that this is related to similar phenomena in proximate antiquity: none of the religions of the era of Sumer and Egypt, et al., survived into the new era that starts around 900/600 BCE. This was itself a massive ‘reformation’ so to speak and we can also see the way that monotheism became a vehicle to amplify this process in its (sometimes fanatical) attacks on ‘polytheism’ and ‘pagansim’, the latter clearly the remnants of the previous era or eras. We should note that it took time for this to happen, and the old persisted for centuries into the new era. We see the same with christianity and judaism now: they have been deal mortal blows by the onset of secularism, but they still persist. But we suspect their fate is sealed. We don’t quite see it yet but the same is happening with buddhism.hinduism, so we see that the issue is not the Occident or monotheism. In fact, ‘hinduism’ is a partial exception because it is not really a religion but a collection of multiple histories that persist as ‘living archaeological sites’, and a closer look shows that those remnants tend to simply float down the stream of history as ghost religions. Buddhism was itself a reformation of that hindu jungle of religion and we can suspect that still once again buddhism will suffer a reformation and move into a new era. There is no reason why a still more profound reformation to christianity couldn’t likewise ‘fool the ages’ and persist in a new disguise. But the energy to create a real future will likely move in a new direction. That future is already there in what we all ‘secularism’ which once included reformation christianity but now has been hijacked by atheists. But theism/atheism isn’t the real crux. Secularism has tended to decay into scientism, atheism, and a sort of cultic darwinism, but there are many dimensions to the ‘secular’ and it is not as such anti-religious. Protestant Reformed Secularism can’t be far behind. The issue of atheism is not truly the point: atheism was a good example of the way our tiding works: it was like a detergent that swept away the pop theism of the monotheists. After that the question of theism/atheism probably goes into deadlock given the vague incoherence of the terms: if you can’t be much of an atheist if you can’t define god so the question just ends back in a semantic jungle.