So hard to choose. I can tell you what isn't my favorite is Darmok. I didn't mind the episode..but when you think about it, it makes no logical sense. A lot of people like to hype that episode up, but the reality is society could never function that way.
But but, if I post a meme gif everyone understands it! Sure, but try to explain to someone how to make a semiconductor using only memes. It doesn't work. A species could communicate on a casual level like that, but they'd all still have to understand normal language.
There's no way you could possibly develop advanced science and technology with a language based entirely on metaphor. Also, how do you have a language based on metaphorical references to old stories when you can only tell those stories metaphorically too?
You would need an ancient society with perfect memories to even be able to get to the point of "language of metaphors" and a metaphor for everything you could need.
Languages evolve over time, so I like to think that's what happened here.
but then how do new babies learn this language and what anything means? The language is also super imprecise and just conveys basic feelings or acknowledgments of situations. Even if you developed a meme for every single word and thought everyone would have to be on board, and I don't know if you've noticed on not, it's pretty hard to get a room full of people on board with something let alone an entire species.
Now I kind of want to try, start with an "I hate sand" then a ... I don't know how to make the wafer, heat? "This is fine". Then shadow puppets? with a laser light show?