That’s assuming the human race naturally reducing or eventually dying out is considered selfish in the first place. We really place too much longevity of humans while extinguishing animals for sport.

That’s not necessarily true. The biggest resource constraint on the earth we can’t live without is food and we are extremely inefficient at producing it. Right now it takes large fields of biological crops, but the future might solve that problem.

That's a good point. The more I think about it the more what I said was a way of rationalizing not agreeing with the parent comment. Even if there were no ressource constrains it still doesn't feel selfish to me not to have children.

Every couple can have 2 kids and it would keep the population constant.

In fact everyone having just 2 isn't enough, it has to be slightly higher, even with modern medicine.

That would be assuming that we've not already overshot sustainable population. With every biodiversity marker pointing that we're in the middle of a mass extinction, it really does seem like that may be the case.