We use metaphor so much we don't even notice: joining the fray is a metaphor from weaving we apply to battle, when moving we weave from side to side, and shuttle is another weaving term applied to spaceships! Much of this extending of language has come from poetry; the kennings of Darraðarljóð in the Njals saga made me notice the prevalance of weaving metaphors.
Ecclesiastes is considered a profoundly subversive book of the Old Testament, at odds on many points with the other parts, but I would say the participatory, recitable nature of it explains why it is there, and why it is read both at weddings & funerals, and even became a pop song:
"To every thing there is a season, and a time to every purpose under
heaven: A time to be born, and a time to die; a time to plant, and
a time to pluck up that which is planted; A time to kill, and a time
to heal; a time to break down, and a time to build up; A time to weep,
and a time to laugh; a time to mourn, and a time to dance"
Shakespeare, TS Eliot, Robert Burns & Tolstoy, among many others, reference Ecclesiastes, which would take substantial background to interpret. From Hebrew.
'This too shall pass' and 'Know thyself' are aphorisms that have gone on to influence literally millennia of philosophy and literature, so even though they are first recorded in Persian & Ancient Greek respectively, they are woven into our language.
The Golden Bough is another is another example. Aeneas gave it as an offering to Proserpina to enter the underworld & speak with his father, who
The seeds of life— fiery is their force, divine their birth, but they
are weighed down by the bodies' ills or dulled by earthly limbs and
flesh that's born for death.
Which is echoed by Yeats' Sailing To Byzantium, which influenced Cormac McCarthy's No Country For Old Men (not to mention Frazer's foundational work of anthropology).
Norse, Hebrew, Greek, Persian. We have cultural continuity with these examples, not only translations but context, set in history & culture. How much is enough, to 'get' these? It depends a lot on what a given era or writer would have read, how deep their references run.
I would say where a living culture of (human) understanding exists, it is translatable, with enough study and shared experience between cultures & languages. It might require substantial introduction, introducing new words even (from schadenfreude to bungalow this has alwats happened), & awareness of a body of cultural reference. But humans are fundamentally intersubjective in our communicating, we invite others into an experience we have, and vice-versa, and this is the basis by which meaning is transferred, founded from proprioception, to mirror neurons, to conceptualising example-giving given contexts in modes of life.
Dolphins have recently been understood to communicate with hologram-like sound pictures. Though we know their intelligence is somewhere very similar to humans, we are still a substantial way from communicating with them. We need a Rosetta stone, or perhaps more aptly the kind of analysis that led to understanding Linear B Greek (Linear A is still a mystery). We will need cultural context of example-giving, of the kind junior individuals are given, towards building a shared understanding of context, to ensure correct translation.
There may be qualia unique to dolphin senses and brain structure, but I would argue they can be simulated, and switched between, by both species, to build a shared cultural context that can access the thoughts of both species.
Dead languages, and extinct species, we cannot access, if we cannot find continuity of lived understanding, like the Rosetta Stone or Linear B examples of shared experience, or later inheritor & interpreters of that culture.
Even puns & rhymes can be given background, and layers of explanation to how they are experienced by native speakers.
Dongshan was asked "What is Buddha?", and answered "Three pounds of flax." I learned recently this is the amount of fibre to weave a monks robe. Koans are often considered untranslatable, potentially meaningless to the 'unenlightened'. But really, occur set against sophisticated theological debates, as experienced directly by a student. Koans began as 'Transmission Of The Lamp' genre phrases recording the moment a patriarch demonstrated their capacity to inherit that title, and show their ability to keep alive the spirit of Zen, in resolving the contradictions they have encountered.
There are many texts which have not been translated. There may be very few speakers of both languages across some cultural divides, or scholarly enough in. I see problems with translation as more of these kinds, than as fundamental.