I would really like to see this type of thinking applied to the movie/short story the Arrival. The whole story is about the challenges involved in learning unknown languages and communication. If we ignore that, there would be no story, or a very very short one.
It's not a universal standard. It's just something that is used and accepted in certain types of story.
As mentioned, it all depends on the type of story you're telling and the logic of it withing the context of the world. Dr. Who is high adventure. It ignores certain things like language translation, butterfly effect, etc. to tell a fun story and have an adventure. It's a basic ask of the audience to suspend disbelief in this instance in order to not bog the story down, especially in an episodic format.
Things like Bable Fish translate from one known language to another known language and even then, it's flawed. They don't translate an unknown language to a known one. They can't because it doesn't know the grammar of the unknown language. It doesn't know the what any of the symbols mean. There's not always a one-to-one correspondence between languages. For example there is no letter-A in Chinese. This is why the discovery of the Rosetta Stone was so significant. It opened the door to translating Egyptian hieroglyphs.
