The situation isn't really a lack of jobs, it's that younger generations don't want to work the factory jobs (because they all studied for better jobs) and there is pressure to look after parents. Not only is there an imbalance in young vs old people due to the one child policy but China also passed a law that required children to provide mental and financial support to their parents. Some parents are effectively paying their children to look after them, thereby removing them from the workforce count.

https://www.voanews.com/a/china-elder-care-law-a-struggle-for-one-child-families/1704200.html