And WW1+WWII are rapidly fading from living memory.
There's the advantage of actually being filmed and photographed extensively, but that only goes so far, especially as our cultures become more and more media saturated.
As the cultural trauma of those wars fades, so will their effect on culture. It'll probably never disappear, but to most young people these days, the 2020 lockdowns are a lot more relevant than WWII.
Beyond this, I don't agree that the World Wars are the root of the shift towards agnosticism and atheism. That'd started long before, and is no small part of the cause of the second.
Living memory, yes, but as you said and unlike in other periods in history, everything has been well-documented because of innovations in media e.g. film, audio, et cetera. That alone changes things compared to prior wars, as it fully exhibits how destructive both Wars were.
Although seeds were planted in the past, and there were even major events like the French Revolution in play, Europe predominantly remained Christian up until the First World War. The death and destruction was, at the time, unparalleled and to an extreme not even thought possible.
It basically killed people's faith in the Christian God, and broke Christianity in Europe.
The Second World War, one far more destructive, coming less than two decades later was the death blow that caved in Christianity's influence as it had been. If there hadn't been a Second, Christianity may have likely recovered in a century or so, but II was the death knell.
Anyway, more and more people are becoming atheists or agnostic, despite the original causes coming up over a hundred years ago now -- the echo has outlived the initial sound, and that echo is continuing to affect Europe.
Unless something Biblical happens, like an Angel descends from the Heavens, there's
zero chance of a religious revival to bring Christianity even remotely back to how it had been pre-WW1.
Some people, especially young people, are finding religion? Good for them. If it works for them, it works for them. But they're basically either outliers or in a minority compared to other people who are looking at religion and going, "Yeah, nah, this is a crock of shit".
So, yeah.
It's not gonna happen, and religion, while the bonds and family structures and support networks it creates are essential to us dumb apes, isn't the magical silver bullet people think it will be to the current plague of utter shit wrecking Western civilization.
Edit: And, to be frank, religious people saying things like "all Atheists are Satanists" or "all you need is God" or variations along those lines? All they're doing is reinforcing the "religious nutjob" stigma they have to the broader, non-religious population.