Self-selecting, if you will. Not to mention, if your society doesn't propagate, others will. Which means whatever your values are, good or bad, they will still be lost and replaced with the values of the society which propagates.
Most advanced countries do not have a self-sustaining birth rate (above 2.1, the replacement rate). Some are able to make up the difference in immigration, but immigrants assimilate and then the birth rates go back down.
