Unironically yes because most of these countries‘ population is sick due to low hygiene and water qualify.
Why do they have a young population? What happens to the old people who live in those countries? Why would that not happen in the receiving countries if enough people are imported?
They have a young population because their birth rates are much higher than in (e.g.,) the U.K.
In 1950 the birth rates in Africa were higher than today. Where are those old people?