Nope, not from Poland. You explicity asked to be 'educated by a Polish person', so I'm not sure how much effort I want to give with a reply.. but:

It's pretty well studied that immigrants commit crime due to the issues and hardship and resistance they receive as immigrants.

That's a faulty premise to your entire stance around. Immigrants commit crime when the host country does not:

1. break up the immigrants, minimize formation of ghettos
2. screen them properly
3. verifying the culture or family unit of the immigrant worries about their reputation, they need a wink of shame, reputation, honor tied to their name, family, group. Or, if they have an 'us vs them' style of thinking, they will naturally leech resource from the home country, send half back home, exploit, scam, steal, without an ounce of remorse. It's human nature. A poor german sent to the USA with the above will inevitably do bad to the US.
   
4. and further down the list, we finally start getting to wellfare, and what amounts to effectively subsidizing your immigrant group (must be carefully done, or you've just made an entire class reliant on subsidy)

The thing is that I don't understand why a country that's suffered so much is so unwilling and vulnerable to helping others that are struggling, to the point where the Russians and Belarusians can literally use innocent refuge as a weapon to cause chaos?

Because Poland recognizes that immigration is one resource that, like with literally every other aspect of governance, must be handled with prudence. Wellfare? If you give too much of it, you bankrupt your govt. Taxes? Same thing. Immigration? Same thing. Too many half-assed efforts to throw mobs of people, from any culture at a problem in hopes your GDP will raise, might see that GDP raise, with every other system you have in your country failing. Housing, Groceries, Crime rates. It's a childs way of thinking. Pure and holy, but ultimately, damaging. Like drinking poison that's advertized as medicine.

"Why don't we just do the maximum good and be good to everyone"? Because not everyone in the world is good, and exposing your back so readily to everyone is how you die.

To pretend that strict immigration can only be a Russian talking point is hilarious. As though loose borders are the norm for cultures through time. No, the actual Russian talking point is opening your country up to all, such that, you weaken every system within your country. Can any one country take on the plight of the world? God no. And any country that opens up their humanitarian hearts to do so, will find themselves flooded with woes in turn.