The episode title 'Et In Arcadia, Ego' (And here I am, in Arcadia) tries to elude what confines in it: That all the main characters have finally arrived to their final destination: Arcadia. Arcadia, the mythical paradise of the Eclogues, represents a final place of happiness and peace. But what Acadia has to do with Picard (the series)? For Picard (the character), whom I believe is the Ego in the iconic phrase, Acadia is the (idyllic and Melancholic) place where he hasn’t gone before. A place to fulfill his destiny. A place to die in peace.
The iconic painting of Nicholas Poussin of the Et in Arcadia Ego theme, the shepherds contemplate a tomb with the phrase written and where one of them traces the words with his fingers. The tomb, a reminder of the presence of Death, as a kind of memento mori, expresses the melancholic feelings of the shepherds.
The phrase Et in Arcadia Ego is also present for explorers, not of a far galaxy but, of the South Pacific like Claude Levi-Strauss (From Tristes Tropiques), as a theme where his melancholy -for being far from his home- distracted him for being in archetypical paradises where he shall die.
Similarly, Arcadia, emerges for the rest of the characters wrapped in complex kinds of melancholy, as an elegant solution for the upcoming denouement. i.e. Raffi's love melancholy for Picard, Narek's wrestled melancholy between his race and the synths, Soji's heroic melancholy to overturn the 'Destroyer' prophecy, Sutra's religious melancholy for survival of her 'race'. All, together, prepares us (the audience) for the final act while we ask ourselves the pertinent question: "Will Picard and his motley crew die at the end?" The only missing link (melancholy) belongs to Rios who seems to be the one with five extra guts to untie the galactic knot.