Low birthrate seems to be common with middle class societies. Asian people now have entered their consumerist, materialistic, individualistic, hedonistic era. You hardly want to sacrifice when your main thoughts are: buy car, career, travel.
The only hope are the underprivileged classes, who are accustomed to sacrifice, but are unable to support their children because of the enormous increase in the cost of living, education and health care.
A government that really wanted to reverse course should help people economically by providing an income from birth to the child (expendable only for food, education, health care).