The thing that's always bothered me about that metaphoric language is that to learn it you would need to be told the stories the metaphors refer to, which means there would have to be a more basic language for telling the actual stories. Then the metaphors would make sense. Same as understanding "gaslight" or "dog whistle" etc.
There was a great thread on Daystrom on Reddit about this. The theory is they have 3 languages. Basically, the bare function words taught to children and in which the stories are told. The main language of metaphors with which we are familiar. And a language of technical jargon. Until they have learnt the stories, language A can be used as a general purpose language for children, but it would be regarded as baby talk by adults except when used for its functional purpose in telling metaphors. The jargon would be necessary even at higher levels.
Holy crap! Except for the technical language this is the exact theory I came up with.
For amusement here's my theory of why TNG Klingons don't look like TOS Klingons: The Klingons first acquired warp drive from some unfortunate alien scientists who landed on their planet. The Klingons killed them and copied their technology, immediately conquering and subjugating every nearby system they could find. Like the ancient Romans, they expanded their empire beyond their ability to govern it. Logistics problems and power struggles on the home planet left many troops stranded on frontier planets, where they eventually settled down and went native. By the time the central government got its shit together and reasserted itself, generations of interbreeding had created Klingons who hardly looked Klingon anymore. Being on the fringes of the Empire, these were the Klingons Kirk's generation interacted with, who are seen in TOS. After years of infighting over the status of the "halfbreeds", the matter was finally settled. Certain distinguished warriors were allowed to undergo modification to look more "normal" - as we see Kang return in TNG. To a racially proud civilization this entire affair is a source of tremendous embarrassment - so as Worf said in the DS9 tribble episode, "We do not speak of it."
I think this theory got trashed by canon at some point, but back in the 90s everybody I told it to thought it was a totally reasonable explanation.
I bet they only talk that way in the presence of outsiders. On their own, they must have a basic structured language while also utilizing metaphors memes where appropriate.
Panel 1: Reference to the TV show Letterkenny ("Let's get on with it")
Panel 2: Reference to old TV ads for Tombstone Pizza ("What do you want on your Tombstone" i.e. "Any last requests?")
Panel 3: Reference to Futurama episode: "Brannigan, Begin Again" ("Yes. Tell my wife how I feel about her.")
Panel 4: Reference to the movie, The Princess Bride ("Yes of course, I'll do that.")
Panel 5: Reference to the movie, Blade Runner ("Time to die...")
Panel 6: Meta reference, sticking with the referential nature of the dialog instead of actually rolling credits.
I'm not an expert on these old stories, but I'm pretty sure they're referencing a movie from Earth's past at the end there. I've had the computer reconstruct it.