NASA appear to be showing a profound lack of ambition. They’ve gone to the end of the world, and will never go further.
For there is no destination more remote than Thule, the semi-mythical far northern land of tales of the ancient world. A mythical character that leaves it open to being identified with a range of different northern isles known to modern man, but always the end of the earth.
Iceland is by far the biggest candidate on the modern map, and tales of a land of fire and ice like Weelkes’s Period of Cosmography (from around 1600) support that. And if Thule is Iceland, Ultima Thule could be either even-more-inaccessible Greenland or merely inflationary language. But only because Renaissance Europe’s exploration had gone further than the Odyssey in the 2000+ years since ancient Thule.
Now NASA has gone to Ultima Thule. The end of the world. By their own choice of nomenclature, they can go no further.
Period as in punctuation: the ultimate end of the world!