Westerners so enthusiastic about “China’s demographic problem” would be well advised to worry about their own, local sub-replacement birth rates, in particular for natives (you know, the ones who built the countries everybody else seems so hell-bent immigrating to), as well as for the educated, the middle classes. Also: https://news.ycombinator.com/item?id=19095925
And many (most?) Western countries do provide various incentives to have kids, as well as Asian countries, but the incentives don't ever seem to work to get above that 2.1 replacement level, so Western governments are 'worried'/concerned about birth rates, but boosting them significantly not an easy thing to do. Especially when part of the reason might be that people simply don't want more than 1 or 2 kids these days regardless of finances.