I tend to not believe it when people talk about whole societies not being religious. I’m much more prone to believe in societies that are between religions rather than truly post religious.
Most people most of the time seem to function better when they accept some kind of system that sets out a series of ultimately unprovable assertions that explain the universe, the person’s place in it and provide (sometimes ludicrous) guidance for becoming a better human being (which can mean lots of society dependent things). That’s not the reality I would prefer to live in, but it seems to be the one that you and I do live in.
Too much religion (any religion) leads to demonstrably terrible results but too little religion doesn’t seem to be any better as it quickly leads to nihilism and demographic collapse.
While many westerners have rejected traditional Christianity they are working hard to create new systems of menaning based on new, still unprovable assertions. The great P.D. James was the first (that I know of) to describe “Anti-racism” in the UK as a new religion (though she might not have been completely serious at the time, her description is still startlingly apt). I’d say that anti-racisim (aka diversity/multi-culturalism) is .one facet of an emerging comprehensive belief system. Veganism and radical vegetarianism are another (turning the simple act of eating mini rituals of righteousness). Modern feminism has turned into another facet (by shrouding sex in an aura of danger and mystery with complex protocols to be followed). Climate change is yet another (calling for restraint and smaller lifestyles in the name of cosmic balance). All seem to be pieces of a bigger puzzle, mainly lacking a central narrative (that I know of). But the sum total of all these beliefs is very close to an unprovable comprehensive world view with something like original sin (at the etho-national, sexual and even species levels) and promote paths of redemption through repentance and proper practice.
Libertarianism (and Neoliberalism) are parts of a competing religious worldview but a less complex one since believers are more likely to belong to a traditional religon.