Religion and cultural evolution - - - -
One of my intellectual guiding principles is: "Nothing in life makes sense except in the light of evolution".
If we treat religions as natural phenomena, and if we look at their evolution, we are tempted to view them as mental "parasites" which spread to the detriment of their hosts.

But if we look at the relationship parasite/host in biology, we always see an evolutionary arms race: the parasite has to change a lot in order to outwit the defense of the host. We see on both sides mutations that give a temporary advantage is this arms race. Just to remind you: a parasite, i.e. the virus, whether in biology or culture, survives and spreads at the expense of the host, who in turn suffers a loss of fitness.

If we now look at the relationship of the human mind on the one side (the "host" ) and the religious ideas on the other side ("the parasites" ), we do not see any arms race so common in biology. On the contrary: the religious "parasites" are among the most stable elements and features of culture! Everything else changes faster: fashion, custom, technology, political systems, money ... even languages change more than religions. Some of them , like Hinduism or Catholicism have not - or only in details - changed for many centuries.

And if we look at the hosts (= human minds and societies): Where are the mutations that "try" to get rid of the parasites? If religions were detrimental we would expect atheist mutations popping up throughout history and then spreading through societies. True: there were some atheist mutations in Ancient Greece and Rome (Cynics, Epicureans, Stoics) - but they just fizzled out, without any suppression from the religious defense system. What we see in history are new religious sects, but they are not the "counter-strategy" to atheist mutations that threaten to provide immunity against religion.

What we should expect too is a decline of host fitness. Again it is rather the opposite: religious people get - on average - more children than the nonreligious.

The conclusion is that the analogy "religions = parasites" is not really adequate, because we do not see any of the features of an arms race we would see if religions were "trying" to parasitize human minds:
no atheists mutations for the most parts of human history; no religious mutations trying to outwit mental or societal "defenses";
no arms race whatsoever.