It is. Infrastructure, strong simple institutions simply do not exist.

And these people brain drained for a while and coming back later is better for those countries.

Do you have any actual examples or research? Remittance and charity didn't exactly help East Germany prosper after the mass exodus of its young, professionals, and farmers...

Oh I am not talking about remittance.

I am talking about emigrants that come to more developed countries and then going back afterwards.