TL;DR: In a plot to destabilize the EU, Putin and Lukashenko personally and directly caused masses of people to migrate from the Middle East, Asia, and Africa, so Poland won't observe the legal right of asylum anymore. They also decriminalised shooting migrants "in self defence".
(Edit) This is from the new, supposedly less fascist Polish govt lol
Russia already does welcome immigrants. Besides immigration isnt an inherently good thing. Its only valuable for free market capitalists.
What are you talking about? Only valuable for capitalists? If anything its MORE valuable for socialists. Immigration is a net positive unless your a xenophobe. It brings in new people many of whom are already educated so you get all the benefits without having to pay to educate them, and even the ones who arent as educated still are really hard working people who contribute a lot to society. People who arent go getters dont travel thousands of miles for a better life. The only real challenges presented by a lot of immigration are logistical in nature and socialist economies are better equiped to meet those challenges than capitalist ones. Plus even outside the economic benefits they bring with them diverse cultures and foods which make life more interesting and fun for the people already living there. One of my favorite things about America is all the different cultures and foods you can find there. Immigration only becomes a problem when you treat it like one and start treating the hard working people looking for a better life like criminals and then force them to turn to criminal acts to make ends meet. If you welcome people with open arms and provide them with opportunity then its only ever going to be beneficial to everyone involved.
It's true that immigration can have downsides for workers if a) you are in a neoliberal capitalist shithole, and b) if you have zero solidarity between native and immigrant workers such that immigrants are allowed to be abused and super-exploited as a consequence of their more vulnerable status.
The way to fight things like downwards wage pressure resulting from immigration is through worker solidarity, unionization and other forms of collective action and organization. And yes this is possible to do with people of immigrant background too; after all, in today's day and age, with the technology available, language should be no barrier to organizing together. The only real barrier is racism.
Standing up for the rights of migrants and fighting for the rights of native workers, these are deeply interlinked struggles and the success of one will always positively affect the other. Throwing migrants under the bus in hopes of bettering native labor's position on the other hand is always going to end up having the opposite effect: it empowers capital while it atomizes and fragments the working class.
That's not to say that massive migration is necessarily a good thing. While migration can have very beneficial effects on the receiver country it is often detrimental to the countries of origin which experience brain drain and loss of the most highly trained labor. We also cannot forget that highly unbalanced migration is always caused by something being very wrong and pushing people to feel forced to leave their native lands, something which most people would not freely choose to do under normal circumstances.
Whether it's war, economic deprivation or ecological disasters that are causing this migration, those causes (most of which were brought about by the same neoliberal imperialist global system that also seeks to profit from turning native and migrant labor against each other in order to better exploit both) are what we should be looking at and helping those countries to tackle. We should not merely be shutting people out because that does not fix the problem, it only causes more suffering.
We are Marxists, we have to take a holistic view on these issues and not deal with them in the simplistic, un-dialectical way that a liberal or a fascist would.
It is inherently good for the receiving country actually, more people = more labour power. It is bad for the country losing these people.
Honestly IMO I think Russia and the BRICS nations could be a step towards the direction where these immigrant populations are more of a boon to their original countries than not. Russia and China in particular are two countries that could be and are doing a hell of a lot to not only export their economic/industrial model (and also collaborate academically, etc) abroad, but also bring people from around the world to see it in action, to see the culture, etc, and develop ties with them firsthand.
People are not just "lost" once they leave, and that this has often been the case is absolutely intentional by the west (destabilization, imperial plunder, etc) making the migrants' home countries destitute and dangerous in comparison, etc. And the knowledge of development and connections between people can absolutely be exercised for good and the benefit of both nations involved, particularly when they can return to their home countries with the assistance and support in recreating or building upon what they saw abroad (something the west has always interfered in on their part).
Both countries are working extensively with the global south, China with its countless BRI/etc projects and Russia as well in its Soviet history as well as presently with security assistance, debt relief/etc, and even helping build a nuclear power plant in Burkina Faso as one highlight that comes to mind (I'm sure there are others, just haven't looked into it). There's no reason that all this training/experience/etc could not be increased with talent coming to these countries to study, or with large student/worker exchanges to really develop a culture of solidarity and multipolarity. And if people wind up staying- particularly those from much less developed or unstable countries- there's still no reason they cannot be to the benefit of both countries in facilitating increased trade and cooperation, or even returning with Russian/Chinese/BRICS/etc support in due time to further develop their home countries in the end.
IMO while you're not entirely incorrect, you're thinking of things n the zero-sum model the west has imposed upon the world- there are other opportunities available, and the Soviet Union's history of doing similar, or China's presently (both without the mass immigration bits, though some immigration did and does occur) are examples of it. It's a more complex and in the short-to-medium-term, more expensive process than the western way of doing things, but I think the end result will be far better for everyone involved.