We have enough people, especially now that we are entering some form of second stage of automatization with AI developments. We’ll be fine if we end up being a few billion less.
What we should be aiming for is a more steady state economy, and not one that relies on endless growth (outside of like, new technology and gathering knowledge). Even today there are so many jobs that could be eliminated by more sane resource distribution, like eliminating fast fashion, building things to last, etc.