The population of Earth has doubled in my lifetime. Population growth is only slowing if you exclude brown people and focus on countries that 1)are wealthy and 2) don't allow immigration. These 'demographic bombs' are the result of jingoism, immigration controls, and racism; they are entirely artificial.
Slow population growth is a crisis for capitalism not humanity. This is because capitalism requires infinite growth and the biggest engine that sustains that delusion is population growth. Just look who is freaking out about it.