collapse of the old society

Wouldn’t it be better for the environment and create less long term suffering to just eliminate humanity?

That would literally be the point of not having kids. Making the decision to be the final generation. No more humans, no more industry, no more pollution and deforestation. The world would not only start to heal, but heal faster without us in it.

As you say, Greed is the root cause. And who is greedy? We are! That makes us the root cause.

any good not having a child solely for the sake of the environment may have is dwarfed by to good a child raised to care about then environment can do.

If there was any truth to this, the world would be a utopia at this point. But no, because we are unrepentantly Human. There is only one way this ends, we go away. Willing or not.