The problem is, policies are about generalisation. Otherwise we couldn't make any laws at all. It's not realistic to evaluate person-by-person millions of people either. Especially when you take into account that 2nd and 3rd generation immigrants are usually more problematic than parents who actually did immigrate.

„Work“ is not always beneficial-to-society work. Especially if you have a good safety net. Even in my country break-even to pay more in taxes than you get back is above minimum wage. I'd expect it even higher in Denmark.

I don't know which are more doomed. Countries who don't „accomodate“ immigrants, or countries who let them in and fail into assimilate.