Not everyone can be a computer scientist, or work a desk job. That is not how society works (right now). If you have farmhands, for example, that are already barely making enough money to live and you import people who make on average five times less in their own country than the new country (and they are actually forced to work), you are putting the poor of your nation deeper down the hole. Being poor isn't usually a choice. Life comes at some people harder than it does for others. Some people get unlucky. Some people are just stupid. Yes, some people actively put themselves in the situation of being uneducated and with little alternatives, but that is not the point. I don't think it's right to punish your country's poor in this way, especially for the sole benefit of people of some other nation who are almost unequivocally going to care less for the nation than the people they are replacing. Of course, in Poland at the moment there seems to be plenty of jobs, considering about a million Ukrainians work there, but that might always be the case.
tl;dr- no, it ISN'T the immigrants fault, but nonetheless it punishes the poor in your country for seemingly no reason, so why accept them in the first place? (<--- the real thought provoking question)