Lack of population growth is a sign the economy is manipulated far below natural level.
Humans get better at doing shit as time goes by. This should support more future humans. If somehow the productivity growth caused by people getting better at whatever it is we do is insufficient to cause family formation and population growth, assuredly either the economy is rigged or there has been some catastrophic change in the reproductive capacity/desire of mankind. There are plenty of resources available to be utilized to support a much much larger population than we have on earth today.