That's an interesting perspective, that could be used as an argument by both camps. You say more social democracy, someone else might say, more social cohesion due to shared cultural background and low immigration.
Social democracy is orthogonal to immigration policy.
You can have welfare state with close or open borders and anything in between, and you can have libertarian state with close or open borders.
For the last few years most EU countries have been going towards pretty strict immigration policy but not towards libertarianism.
Also Poland is not a good example (it's been accepting A LOT of immigration since ~2014 - more than average in EU). But that argument gets pretty detailed very quickly so unless you want to go into it - I'll leave that alone).
