I know people who don't have children, who I can't think of as selfish. And others who are clearly selfish. There's all kinds. Those who don't want children should at least be thankful for to the ones who take on the job and do it well. I can understand the resentment for the parents who raise kids to be worse than themselves, that's a shame, and it happens a lot.
Bingo (BCP). If nobody was reproducing society would die a miserable death, would close in upon itself. People get old. Germany is having a problem with insufficient reproduction rates thus has to look at other (perhaps unstable) options. Successive generations are necessary.
I used to think kids were the worst idea ever. Then my wife's biological clock alarm went off and she expressed a few thoughts that made me look at it differently. My thoughts changed to "why the heck did we wait so long?"
My experience is that the enjoyment you get out of life, is dependent on on how much love you share with others. Kids are an bottomless repository for love, and it can make you feel good to pour it out with no limits. This can be viewed as selfish I suppose.