One of the basic premises of anti-immigrant policies is that you can somehow influence the ratio of "useful" vs "not-useful" immigrants. Apart from the idea of sorting people into useful and useless being inhumane, it also seems to be counterproductive. It looks like every kind of screening of immigrants will deter the more desirable ones, as far as that determination is possible on their arrival at all.
How do you think it would affect a country to suddenly have a very large amount of low-skill immigrants? How would the native citizens, the people by which their government is held accountable and to whose interests their government's purpose is to advance, be affected? The answer is probably that they would be very adversely effected, in which case however "inhumane" it is to sort people like this, it is also inhumane to do wrong by the native citizens who built the country that those immigrants would be living in. Immigration is not a human right, nobody has a right to immigrate anywhere and no country has an obligation to accept any particular person or group of people as immigrants.