Multiculturalism can, in fact, work quite well. I live in what the United Nations has called "the most multicultural city in the world." With around half of its population (5.9 million in the greater Toronto area) born outside the country, Toronto is often referred to as 'the most multicultural city in the world.' Located in Canada, this city boasts 200 ethnic groups with over 140 languages spoken. And of course, every religion is celebrated here. I myself have been to hundreds of mosques, temples, churches, cathedrals, Quaker meeting houses, Synagogues, and on and on.
The trick to multicultural success is simply this: it is not necessary to believe every system of belief is good, but to respect the beliefs of others anyway. It is not necessary to celebrate or participate in the rituals or cultural practices of others, but to respect the rights of others to participate in them...so long as they do not fall foul of the laws of the nation, the province or the city. It is not necessary to approve of the sexual practices of those who are not oriented the way you are, and it is certainly neither necessary nor recommended to participate in them! … but permit others the free use of their conscience!
This requires a certain amount of accommodation, but we in Toronto have not found that particularly difficult, and in fact, we go further and have many annual street fairs and festivals that celebrate all sorts of traditions, and a very large number of Torontonians of every race, nation of origin, language and religion attend a lot of them. I certainly do. Large Canadian banks and other corporations, and governments, have been providing family benefits to the families of their employees, even same-sex families like mine, since before our nation adopted same-sex marriage.
Some accommodations are admittedly difficult for some: the Mulsim cab driver who won't accept a dog in his vehicle because he considers it "unclean" is going to have a hard time keeping a job with any of our major cab companies. But that is not unreasonable: if he can't deal with the customers, he's in the wrong business and needs to look for something else.
Edited to add: I'm reminded of the problem of the baker who wouldn't make a cake for the wedding of a same-sex because he religiously disapproved of homosexuality. But guess what, baking the cake is neither approving nor disapproving...it is merely providing the service that you offer. Doing your job, in other words. The plastic surgeon who provides a cute button nose to someone who wants it many not think it looks appropriate, but as long as there's a consenting adult who wants it, well, that, too, is just providing the service he offers.