Multiculturalism as the word denotes, means several cultures.  When we speak of  immigration we expect able bodied people from different regions of the world.
What we're getting now is mostly from one region of the earth that would not  want to assimilate, therefore the word 'assimilate' is transformed by the media as an insult to the new arrivals, hence the culprits tend to  confuse the readers with narratives of the success using the word  'multiculturalism', as from several cultures, not a particular one.