@Bontonbonbon
"Japan experiences this well before we did because they had earlier access to the technology. Their falling birth rate is fuelled by two things: the high cost of living and growing numbers in two generations of people opting out of society to live in an online world."
It is true that high costing of living is one of the reasons birth rate is falling, but you're wrong about the technology side, if anything what you said about technology is inverted.
One thing with Japanese culture is that even now it's extremely sexist with massive focus on gender norm and social expectations, plus shame culture, you need to marry and have a family even if it's an arraged marriage without any love.
On the side of men many effectively live to work themselves to death, especially if they're salary man, they pretty much don't participate in their children life, sometimes not even wife life, because they work so much, and if any of you don't believe me google "Japan black company".
On the women side they're expected to have children and become housewives, they don't have any support to put their children in daycare and such, they have to become housewives and their lives will be 100% about taking care of the house and the children.
Women expectations are so bad that many effectively don't get promoted at their jobs because everyone expects them to marry and stop working altogether, never getting back at it, and just to make a point, any of you search "Japan medical school scandal", multiple universities literally rigged the exams so women would fail, because they believed most would eventually stop working to have children, with some even saying they only entered med school to find husbands.
Japanese people started to get into online world because that's literally all they could do since they had no life besides work or take care of the house, it's one reason for example Japan has a massive amount of mobile games, gacha in particular, because you can play it anywhere at any time if you have 5 minutes free, because they simply don't have time to something else in their lives a lot of time.
Another reason young generation don't want to marry isn't just the high cost of living, but because many simply don't want to live like that, Men don't want to work themselves to death but have no choice, so they stay single because at least in their free time they can use their own money for themselves, women don't want to marry because they don't want to become a housewive and have no future besides taking care of the children.
Also, unlike in the west women are expected to completely be a housewive for the rest of their lives and have no career, at best most get a part time job because it's all they can do, it's not like in the west where women have a lot more freedom.
Japan has a lot of social problems that justify the declining birth rate, technology and smartphone ain't even close to be one of them, a lot of people throw themselves at online world exactly to escape the crushing expectations of society + many times it's all they can do with the little free time they have.