Birth rate decline is caused by cultural and economic factors both. The reason people had 5-6 children back in the day was both because of herd mentality - everybody else was doing it - and because in agricultural societies, children were an investment for the future. Now, economies are structured such that children are an expense. The two factors are mutually reinforcing; the more people believe that children are a drag on their modern life styles, the more they influence others to see it the same way.The later part of your post underlies the problem with blaming feminism for the decline in birth rates. Saudi Arabia, Iran and India are all not feminist countries yet have experienced a massive decline in birth rates.
On a similar note someone else mentioned a decline in marriage rates being a cause. Again countries like Saudi Arabia and Iran have very high rates of marriage. People in China, east Asia, the west (and much of the world) are still getting together, they are just not having children.
Btw, secular Israelis are not much more economically productive than the Haredi. The reason the whole country works is because of the massive amounts of aid they receive from America, the EU and the diaspora.
To slow this decline in TFR requires that you make progress on both ends. Children must not be treated as an economic burden because they aren't - they are a necessary investment for the future of the nation, without which national extinction is just a matter of time. To this end, governments must address the economic root of the problem by investing in the nation's future and not just "paying people to have children" but actively making it so that children are the most reliable way to secure retirement.
At the same time, the culture must change, both extreme feminism and extreme materialism are aspects of the Western/East Asian "death" culture that should be discouraged or banned from Chinese social media. People who keep spreading the toxic idea that family and children are backwards/old fashioned should get canceled. Compared to the sort of **** that get people canceled in the West, there is much more justification in restricting people whose influence is actively sabotaging the Chinese nation. These are the minimum that must be done for China to have a chance in the future.