Of course, from the position of empathy, it is extremely sad people don't commonly adopt children, and I would welcome everyone to do so - along with having their own. Adoption is important to give everyone a family and save them from the horrors of orphan life. New births are important to keep human population stable and the world continuously running.

As much as I want to only come from the empathetic "adopt first" (and I consider doing so myself in a not-so-distant future), we have to have other considerations as well if we don't want to live in a dying world where everyone - from kids to seniors - faces insane, never-before-seen economic crisis, destroying life for everyone. It already gets worse, and we only dropped fertility a little. There are objective economic factors to this, not only capitalist greed (which, however, is also present).