in places like France, and id bet many others, theyve made no attempts to assimilate. they tried to have their cake and eat it too. we want the cheap labor, but you have no path to citizenship. so.....you've invited large numbers of people into your country who are forever, by law, an underclass.
many muslim groups likely are difficult to assimilate, but IF you're going to bring them in, then its foolish to make 0 attempts to assimilate them. then claim that "they wont assimilate" lol.
and as for bringing other groups in.......who? you invite the cheap labor in thats close to you. no one is going to fly poor rural chinese into their country. that would be political suicide. so some countries basically say, "if you can make it here and work, we'll take you."
those numbers could very well be right, but where are you getting them?
and europe has never been homogenous lol. its one of the most ever-changing regions of the planet.