It seem clear to me that Men of the past could believe all kinds of wrong things (and even have massively contrasting religions), without coming to serious harm.
There was a very broad area of what seemed like common sense that meant almost all people, everywhere, shared broadly the same ideas of The Good.
But that now wrong ideas, and almost any wrong idea seems to suffice, leads to the grossest evil of value-inversions; such that people nowadays consciously, actively and strategically pursue lies, ugliness and sin (and persecute truth, beauty and virtue) in ways that simply did not happen in the past.
The best explanation for this difference of which I know, is Owen Barfield's account of Original Participation.
What this suggests is that originally Men were spontaneously, and mostly un-consciously, immersed-in and controlled-by the divine and spirit world - from birth and through their lives.
This influence came-through in all kinds of natural instincts; and these instincts shaped all traditional social practices - without awareness or planning.
These ancient Men were less free, less consciously aware - and they just accepted and followed all kinds of behaviours which - ultimately - derived from the nature of divine creation. Men were mentally part-of divine creation, and therefore what they thought and did was broadly concordant with divine creation.
However; across the ages and through the centuries this has dwindled.
Men have become more conscious and autonomous of the natural and created; and in recent generations the immersive and unconscious, instinctive, controlling link between the divine and spiritual, and each Man's thinking, has been all-but severed (except during early childhood). We are cut-off from God and divine creation.
This phase we currently inhabit is what Barfield calls the Consciousness Soul; and it explains why bad/ wrong/ evil ideas now have such a devastatingly inversional and weird effect on individuals and societies.
There is still a sense in which we all still already-know (naturally, spontaneously, instinctively) what is Good (i.e. true, beautiful, virtuous, in harmony with God and creation) -- Yet that knowledge lacks the automatic regulatory power it used to possess. Instead, we are often deeply suspicious of this innate kind of knowing.
At any rate, such knowing is far more easily confused or over-written than ever before in history - often as a prelude to its inversion.
If all this is so - what does it mean and imply?
It means that, in some sense, we can and should return to living in harmony with God and creation and in connection with the world of spirit.
But it does not imply that we should recreate the behaviours and societies of the past. Indeed that is strictly impossible; since we are now so utterly, radically, different from the Human Beings that used to inhabit such societies.
A society based-upon the natural and spontaneous connectedness of people to God, cannot happen when people are - as a matter of fact - Not spontaneously connected to God!
If not, then what? If not the impossible reversion - how instead might we move towards the harmony with God that Christians desire? Well, one helpful step is to identify and correct wrong ideas of our own.
The fact that these wrong ideas were (pretty much) harmless to Men of the past does not mean that these same ideas will not harm us now.
Bad ideas now are widely and deeply toxic to our whole alignment with the world of divine creation - therefore we absolutely need to become aware of them, and correct them.
It's a big job - for a Christian to identify that which used-to-be regarded as harmless, or even as necessary, to his faith - and then reject it as incompatible with the basic aim of Christian life!
Yet something like that, seems to be the special and vital spiritual task of this time and place.