Problem goes away in 60 more years (two generations). Neither the Slavs nor the Greeks are reproducing at anything near replacement rate. Meanwhile, the Albanians are having a population boom. By 2070 there won’t be enough Greeks or Slav around to argue with the Albanians that both northern Greece and southern Serbia (the former “Macedonian” province of Serbia) was part of ancient Macedonia. It will all be Greater Albania.
As distinct from just calling it part of the “Umma”.
Unfortunately you may be right..the once heroic Greeks seem to have rushed pell mell into hedonism and selfishness along with the self destructive impulses of such societies such as those that result in infanticide. As a Diaspora Greek I have seen this spectacle firsthand.