Firstly, why?
Secondly, macro-diversity necessarily means micro-homogeneity. If you insist on everywhere being diverse then everywhere becomes the same slop.
Thirdly, you lack a sense of tragedy. A well-functioning civilised successful society is very rare in this world. What exactly produces the success is difficult to ascertain but radical experiments to change it are not such a great idea.
Chesterton's Gate tells us to be very cautious about changes that upend the very way mankind has lived for thousands of years.
Fourthly, the premise that diversity is a morally good thing only exists in societies with a high openness and high trust. These societies, like Sweden or the UK are vanishingly rare, and through the diversity importation they will cease to be open and high trust. The groups arriving will suffer from "third worldism": clannish inwardness and low trust.
Fifthly, wanting to move to live near White people is not a human right. It does seem like the whole world wants to move to White dominant countries but there is literally not enough room for 4 billion desperate people.
Can you imagine how boring the world will become if everywhere and anywhere has exactly the same population makeup.