Population is one of those colonialist/consumptionism metrics that illustrate how unintentional human civilization (city-based society) really is. The one feature of humans that actually differs from other animals is our actions based on imagined futures. It started with the cutting of stones to make an imagined 3d model of a tool rather than just stumbling across sharp rocks. The communication of that model to our hands evolved into language from person to person.
Civilization shifted our ability to be resourceful to our places into being extractors of resources.
Increasing population feeds this extraction dysfunction and inhibits intentional group behaviour: favoring aggression and competitive consumption via artificial value schemes.
First in/winner take all ensures fewer winners and more losers until there's no more to win.
Collapse is inevitable, but it really isn't the population numbers; it's the backward thinking of civilization's isolation from the environment that spawned us, and the resultant selfishness of our intentions.