After World War I, right after Poland regained its independence, there was a strong movement to restore a "greater Poland" similar to the old Polish-Lithuanian Commonwealth. Pilsudski was a believer in this idea. It quickly ran into the problem that the Lithuanian;s and Ukrainians saw that it would mean political dominance by the Polish majority and instead chose to form their own nations. There was a lot of horrible violence and massacres and Poland created a lot of bad blood with its neighbors.Yeah, I think there was a prevailing unwillingness to assert the sovereignty of nations which had been created through the treaty of Versailles. The German line was always that Czechslovakia, Poland and so forth were "artificial nations" which were created by mistake, and I think to an extent that line was easy to buy for people who could remember a time when those nations didn't exist.
Britain and France were, at the time, the biggest colonial powers in the world. The idea of national self-determination was important in American foreign policy (despite its own "empire" in the Pacific) but I don't think it held the same weight in Europe.
To tie this loosely back to the topic.
I think the most incredible parallel, if true, is the claim by Poland's former foreign minister that Vladimir Zhirinovsky, then speaker of Russia's parliament, made an offer to partition Ukraine with Poland.
You can doubt it (the source has acknowledged it was somewhat overstated) but fact that it is entirely believable is symptomatic of the fundamental ideological differences between Russia and the rest of Europe. Poland, as it turns out, is not hanging on to the idea of creating a "greater Poland" by seizing lands once held by the Polish Lithuanian commonwealth. Russia is very clearly hanging onto the idea of a Greater Russia, and to an age when European states sought to expand their influence through expanding territory. That's honestly a bit sad.
On the western border there was the issue of large German populations living territories that Poland wanted. There were uprisings, battles, foreign mandated plebiscites and in the end Germany got a bit screwed. Areas that under self determination should have gone to Germany went to Poland because the new nation needed them for political, military and/or economic reasons. Interwar Poland was a mess and the nation accumulated a lot of bad karma. It's just that no nation "deserves" what Hitler's Germany ended up doing to Poland during World War II.
In the present time there is a very pragmatic reason why Poland would never want to taken any part of Ukraine. Poland already has a lot of poor, underdeveloped areas and really does not need new land that has been depleted by war and would require massive investment to become economically profitable. If Ukraine survives this war, Poland will have a market for its goods and Polish companies will profit greatly helping to rebuild the country.