Why is this even worth caring about at all?
If these numbers were 20% higher or lower, would it really make much of a difference? You'll never have any interaction with their cultures or people. You'd never even want to visit most of these places even if they were emptied out.
As long as they don't come to your borders, don't mooch on foreign aid, and never get invited in, why should any of these teeming billions be of any concern? They should be just about as relevant as if they were on some distant planet.

I get it but these are two different things.
The key to stopping mass immigration is just stopping mass immigration. Don't let them in under any circumstances, don't give them any aid, and get rid of the people who promote these things.

So cut them off. Get rid of the people giving them aid. Get rid of the underlying incentives to give them aid. And so on.
These are things that are infinitely more possible to modify than whether Ethiopia exists or not.