[user104658]

Not sure if people realise that what they're describing is not "multiculturalism". It's a complete failure to properly implement multiculturalism.

It CAN and DOES work if people are willing to put in the work but the most important factor is acceptance and integration. The reason it has ended up failing so badly in so many areas, the reasons that ghettos and divisions end up forming, has as much to do with lack of acceptance as it does the desire of those who end up there.

Look back over the last 50/60 years, or since WW2 really, and tell me that Britain (average Bob in the average British town) opened his arms and accepted other cultures?

Rejection leads to alienation leads to resisting integration. The exact OPPOSITE of multiculturalism.