When I was born there were 3.9 billion people on the planet and now there are over 8 billion. As someone who is an extreme introvert - I'm not happy about that. You may have read about the world population as being in decline, falling fertility rates and women not having as many children - if at all. But the reality is - the population is still increasing.
There is a carrying capacity for how many people the earth can comfortably sustain. No study has been carried out to calculate this figure. If you consider the requirements for each human being, in terms of food, drinking water, clothing, drainage, electricity, heating, healthcare, pensions, etc. we could put plans in place to make sure that everyone gets their basic needs met. For example you can calculate how much arabal land is needed to feed one person and then look at how much land we have that can be dedicated to farming. We can consider how many houses we can have without overcrowding. There is no such plan in place. The rate that the population increases or decreases is left to run wild. There are no controls in place and life-expectancy is increasing. There does seem to be a 120 year maximum that we have yet to overcome. Our cells can only regenerate for so long. Stem cell treatments may someday get around this issue. We may even learn to transcend our physical bodies - inhabit artificial ones or develop ways to grow new limbs and organs.
There are certain incentives to desire a constant growth in population. The economy for one - More people means more customers. More people that need loans, products and services. Then there is religion. Religions encourage people to have children because they know that it is highly likely that the children born into a family of a particular religion will indoctrinate their children into that same religion. Each religion wants to outnumber the rivals, and it goes the same way in general for different cultures. Muslims would love there to be mosques everywhere and for more followers of Islam. People want there to be more people who are like themselves and less people who are not like them. As agent Smith once said - Humans are like paracites - a plague of this planet.
You might also want to consider the possibilities of sudden large-scale deaths, due to a natural disaster, pandemic or war. I am confident that in any of these circumstances it is highly unlikely that all of humanity could be completely wiped out, or we would reach a point where we are unable to recover our population to the desired amount - whatever that is! Here we hit upon a huge problem - who is to say what the ideal population figure is? You would never get everyone to agree on a figure globally. What about people inhabiting the Moon or Mars? How many people should we allow there? Unlimited?
How many times in the future will we see news pictures of children starving to death? Homeless people living in poverty, because there is not sufficient housing or employment for them. Are we getting closer to being able to eradicate such things? With the emergence of robots and artificial intelligence taking over our jobs - nobody really knows how this might negatively effect the well-being of people. Will we be living like kings in a world of abundance? Or perhaps we will have a world of abundance that all but a tiny minority can afford to purchase. Certainly it seems that a small number of people are getting rapidly richer whilst the majority of people become increasing exploited by those in power.
It seems for the foreseeable future we will continue to blindly keep growing the population. I can't see any controls being enforcable within my lifetime, so I conclude that whilst I don't like the situation, I am powerless to do anything to change it.