We live in an environment of planned obsolescence and mindless consumerism. A high quality of life can be achieved for everyone globally if we wanted to do so. Instead we sustain a system designed to extract 'profit' as it's driving virtue.
Reducing the numbers of humans on earth would not make any significant long term difference. As long as infinite growth is the core principle of the worlds biggest economies, it doesnt matter how many people there are. We would still at some point overstep all planetary boundaries.