London is a very successful and very diverse city. (Just like the USA is successful and very diverse country - and there are parallels...).
In the many periods of London's expansion, the city has sucked in economic migrants from outside its boundaries.
In Pepys's day the child mortality rate was so high that they needed incomers to maintain numbers.
After various plagues people flocked in to fill the void.
Hugenots, Jews and other groups arrived from Europe fleeing from persecution. Irish, Scots and Welsh, fleeing other types of persecution and lack of opportunity.
Charles Dickens writes about it, (in Dombey and Son I think.)
After the second world war, many were persuaded to come here from the colonies to receive a chilly welcome. "No Blacks, No Dogs No Irish" appeared in many a window. Without them the NHS. London Transport etc would have been impossible to run. Their children are now contributing to many walks of life.
London is still growing - you only have to go there to see the amount of construction.
In many ways it is a wonderful place. The election of Sadiq Khan was a bright moment last year, as was the graceful and inclusive way he took up office.
If all the immigrants, children of immigrants and grandchildren of immigrants in London went on strike for a day, everything would have to close. From the Houses of Parliament to the humblest catering outlet. All the hospitals, all the transport and all the offices would be unable to function and do their work.
There is absolutely nothing wrong with this diversity in my book. Any more than there is nothing wrong with the USA being made up of people from many and varied backgrounds and being proud of it.
The only wrong thing is that large slabs of the UK are getting left behind economically. And that successive governments have been too laissez faire in their approach to housing.