Every child born is a "bare illiterate human". Are you also making an argument against having children?
If you want to be really draconian about it, immigration can select for people with skills where the home populate will always have the same average of innate abilities.
Children have a lifetime ahead to learn and grow, as opposed to illiterate adults who are handicapped at that since they are past their prime neurological and societal plasticity.
If you want to be really draconian about it, immigration can select for people with skills where the home populate will always have the same average of innate abilities.