...Muslim immigrants. They hang onto a religiously-driven cultural conservatism and reject the more liberal cultural values of their host country...
As opposed to, say, Catholic immigrants from Poland coming to UK? Or Jewish and Italian immigrants that came to the States in the past? The first generation will very often cling on to the culture they grow up with, but as we have seen many times, their children, by and large, adapt to their new country - if they are not kept out. But if you are met with suspicion and hostility, like for example they Turkish immigrants in Denmark a couple of decades ago, or the refugees now, then it is quite hard to feel welcome, and as a reaction you keep out.
...abandon their cultural and religious practices that were incompatible with their host country or already had a culture and values similar to the host country.
Yeah, they are just not like us, with their murky skin and garlic-breath, is that what you are saying? Why would they have to abandon their identity? That is an absurd and shameful thing to demand, and it is designed solely to ensure that muslims understand that you think they are somehow lower than you. We in the West would hardly feel it was reasonable to have to abandon our culture and identity in a similar situation. You are simply being mean and rather despicable.
Immigrants are people just like us, except they are quite often in a desperate situation. Some may be criminals, sure, but most are fairly good people; they don't expect to be waited on, they just want a small chance to survive, but people like you would rather see them and their children drown in the Mediterranian than reach out and give them a hand, am I right?
Of course we shouldn't just throw open the doors and let them in just like that; but we can much better than we do at the moment. We could, for example, emphasize that a permit to settle is a contract - we let them in and help them get started, and in return they have to make serious efforts to integrate well into society. There is no need to abandon your culture - living in London I know that, at least; I wade knee-deep in mosques, Hindu temples, Buddhist temples, synagogues, etc, not to mention a large number of Christian churches. They don't seem to be plotting to kill me.
But even then what you're arguing for is that Scandinavia needs and wants is economic expansion via labor pool expansion, not that there's something missing from it socially and culturally that the contributions of conservative Islam.
One of the things I hear quite often in the news is that there is not going to be enough of working age to support the growing number of people in retirement. So, we either have to get used to working significantly longer before we retire, or we need more people of working age. Unless, of course, we start euthanising people of a certain age; I am not convinced that this would be popular. So, what do we choose? Do we all work until, say, 75, or do we invite people in, who are able and willing?
As for what may be missing in Scandinavian culture - who knows? Perhaps a bit more self-confidence? Or a wider horizon? Look to UK: they have had a huge influx of cultures and immigrants from all over the world, certainly since the days of the Empire. But there is no mistaking Britishness: it is very distinctive. Immigrants have come in, made their mark, and become British.