It's blindingly obvious that modernity is applying strong natural selection to humanity and that, over time, the world will come to be dominated by the kind of people who have children. In order for that not to be the case, you have to imagine a world without inheritance of characteristics. It's not even necessary to imagine genetic inheritance: even cultural transmission of fecundity from generation to generation would suffice for shifting the distribution of personality traits in the world's population away from whatever depresses birthrate below replacement and towards whatever promotes high birthrates. If you want to know what the world will look like in a few generations, look at who's having kids now.

The "lol seven billion is enough" comments completely miss the point. Fertility will recover once inherited fecundity spreads through the population. One way or another, we're going to hit the Earth's (or solar system's) carrying capacity soon, probably in a few centuries at the longest. Do you want that future era to be full of people like you? If so, you need to figure out why people like you aren't reproducing now.

To imagine that fertility isn't heritable is to deny all of evolution. The drive to reproduce is the oldest and strongest urge of all. It's ubiquitous in the tree of life. It's really bizarre to me that people don't see this dynamic. Of course evolution applies to people: have you ever met a parent and a child?