In fact, global population will likely peak around 2050, and then start falling, which will be a whole new crisis. People will look back at overpopulation fears and laugh.
A rapid fall in population would be problematic, but a steady state or slow gradual decline would be beneficial - and perhaps environmentally necessary.
Obviously you need to ensure there are enough young people to support and care for the elderly, so population can't be too top-heavy. But improving technology (robots, AI) should reduce the need for labour without compromising living standards.
Like for example, look at this Haiti plot: https://knoema.com/atlas/Haiti/Population-density
It is already 1.5x more dense than Germany. 3x more dense than China. Would it stop? When?
Why is Switzerland 9x more dense than Ireland? Is population of Ireland expected to eventually grow to that of Switzerland?