Armenia regaining those lands would be like Germany regaining Kaliningrad.
Bad comparison. Turkey was an aggressor, which got rewarded for its agression and genocide. Germany was an aggressor, which got punished for its aggression (and indirectly its genocide).
Anyway, the point is that it would basically entail massive ethnic cleansing for Armenia to regain those territories.
Which raises the question whether ethnic cleansing can sometimes be justified to reverse the results of a previous ethnic cleansing? This is of course a problematic remedy, but at least in Bosnia I would support it (the Serbs should be cleansed from certain areas which had Bosniak majority prior to the war) and you
could make a case for Eastern Anatolia as well (there are still a couple of hundred thousand Armenians in the region btw although they are almost all Muslims today - for obvious reasons).
If you can never revert population changes successful ethnic cleansing will
always be rewarded. Which is a rather problematic element in international relations.
Turkey got away with the Armenian genocide, slaughtering and expelling the Greeks (atrocities on both sides, but two wrongs dont make a right) and driving Christian Arabs (and Armenians) out of Hatay (and killing quite a few) prior to their bogus 1939 referendum. Modern Turkey is to an unusually high degree the result of successful ethnic cleansing.
Other than that, your comparison with Kaliningrad was simply tasteless, given history. The Young Turks were the proto-fascist orchestrators of genocide and the Armenian Genocide was an inspiration to the Nazis. So the Turks and the Germans are the ones who are comparable in this scenario, not the Armenians and the Germans.