Why the presenter thinks that a declining population is a bad thing reflects an outdated paradigm. Population growth may make a nation more influential on the world stage but it doesn't mean life is better for the citizens of that country to say nothing of the global impact of overpopulation. Getting global population to a sustainable number is essential if we are going to have any kind of liveable future. Doing it through a reduced birth rate is by far the least disruptive method. The alternatives of resource wars, famine or pestilence are all much worse for everyone.

With a declining population there are less people to support social programs, particularly for the elderly. An inverted population pyramid would mean that there are actually more people of retirement age compared to working age. The retirement age in China is 60 for men, 55 for white collar women and 50 for women working in factory jobs. The declining population and unfavorable ratio between the employed and the retired means that the working age population will also have to spend more of their resources providing for prior generations which means that less resources are available to either produce the next generation or provide for them.

China also made a major mistake with their one-child policy. The desire to have male children decades ago has led to fewer women of reproductive age being available now. This in turn has led to more unmarried men who tend to be protestors in demonstrations and riots because of the diminishing economic and social prospects. So there it is a societal impact when controls are introduced to affect reproduction. China is now seeing the consequences of their prior policies and these problems may be more difficult to address than the concerns of overpopulation decades ago.

Today it takes so many fewer workers to produce a "widget" than 20 years ago. (China Labour Productivity Growth data is updated yearly, from Dec 1953 to Dec 2022, averaging at 7.40 %)
https://www.ceicdata.com/en/indicator/china/labour-productivity-growth

Advances in AI and automation are going to accelerate this trend in the future, so concerns about the worker to retiree ratio are misplaced. As far as excess men, yeah the enforced one child policy really messed up that with some social consequences. However, crime rates in China are low so clearly all these excess men aren't going to topple society.

The bottom line is that the proven dangers from global warming and species extinction are a far greater threat to all of us than any of the concerns commonly brought up when declining birth rate are discussed. Furthermore you need to ask yourself why population numbers are never challenged by the global elites. We are both consumers and labor units to the owners of capital. The more of us the lower labor costs and greater the consumption of all the crap they sell us. We can either begin to institute VOLUNTARY birth control, starting with ensuring infant survival (if a woman thinks her kids have a good chance of reaching adulthood she will have fewer children). We then need to educate every woman on the planet to a highschool graduate level (Educated women have fewer children.) Beyond that we can pay women a stipend every year they do not give birth and incentivize men with a payment for vasectomies.

......perhaps less of their "bad air coming over here"? (remember that guy from Georgia senate race)

sarcasm