It would be impossible for Poland to "illegally" annex its own sovereign property, art, and culture.
Indeed, however Ukraine is not Poland's "own sovereign property, art, and culture" and nobody credible has ever suggested that...
Poland's rights are undeniable.
Poland's rights do not extend to invading Ukrainian territory and nobody (except yourself, an American with, shall we say, deeply eccentric ideas) has even suggested that.
To remind you, since you evidently have difficulty grasping the concept, Poland and Ukraine are friendly countries who respect each others borders. Neither sovereign state have any irredentist ambitions.
You remind me a bit of that crazy who used to post here with a similar user name, LegalEagle (which he was anything but) that believed or pretended to believe that Lech Wąłęsa was still president!