Interesting in this context is completely divorced from morally good/bad. Could be any group from any area at any time in history. I’ll start with a few, followers of the cult of pythagoras, contemporary black Hebrew Israelites, antiracist skinheads and the Amish (neo-luddites in general). Don’t be racist or a prick to other people discussing.
I mean more people literally means more technological advancement, more universities, more experimentation, more engineers, more ideas tested and developed.
I’m not sure how you think we would exactly motivate a global depopulation short of something extremely unpleasant aka the example I gave of just charging the actual cost for products and services. Maybe a one child policy and you kill the extra children and one of the parents for breaching the rule. Good luck roping the rich and powerful or developing nations into this. At least developing nations with a high fertility rate will (and do) argue that they should not be punished for the misdeeds of others.