I'm not disputing that articles are sometimes useful, indeed sometimes you need "the" or "that" for disambiguation. But in most cases it's [a?] noise that I can't make sense of as in your previous example.

[I seriously cannot decide whether "it's noise" or "it's a noise" is correct in the previous sentence because it makes sense to put "some" in front but putting "a" "feels" wrong.]

> "The dog opened the door and entered."

Why "THE" door? It's not been previously introduced and it refers to the very door being opened by the dog. SUCH use of articles is confusing and nonsensical when set against all of the examples where "the" _does_ make a difference.

Similar examples: "I'm on the phone", "I'm in the shower", "The food is in the fridge", etc. By the same "rule" that requires "the" in these examples, you should be supposed to say "I'm at the home", which is for some reason wrong.

Next, should one use "the" / "a" or nothing here: "I'm at the post office." [Which one? There are tens if not hundreds in a large city.]

I've learned those and many others as expressions by heart, but use of "the" is a mystery to me.

As for "a", I have two simple rules: nouns (usually) cannot stand naked, and "a" is appropriate if "some" would be appropriate as well.

Or, if I imagine a teacher saying: "Today, we're going to learn about the animals that ruled the Earth 100 million years ago."

Why "the" animals? Why did I put it there in the first place? Because if I read the sentence silently, it feels "wrong" without an article before "animals", yet I cannot put "a" since it's in plural.

Or, even more amusingly: why "THE Earth"? We only have one.

Or, contrast with: "that ruled planet Earth 100 million years ago". No "THE planet Earth". Why? Or is it correct to say "THE planet Earth"? I seriously have no idea.

> “This is not the story of the night but it definitely is a story.” If I drop the articles, it seems I have to re-word that sentence to convey what is being expressed.

If you drop articles, it'd be ambiguous in English because it could be interpreted as "This is not (story of night) [i.e., story _about_ night] but it definitely is story."

The ambiguity in Croatian is resolved by declension; "night" would be in genitive case which seems to be the role of "the" in that sentence.

"A" in "a story" doesn't seem to have any purpose (to me).

EDIT: So, that's my perspective. I can't describe it in a better way than listing examples where "THE"/"A" is somehow required (or, worse, it must NOT be there), yet the use doesn't have anything to do with "specificity".

As an amusing anecdote: A couple of years ago I attended a course on scientific writing in English and we had to write an essay. The teacher returned the essay to me, it was full of red ink, and the vast majority of the errors (like >80%) were wrong use of articles (missing or wrong).

EDIT2: As for my native language (Croatian), definiteness is mostly implied. When you feel that specificity is needed because there are multiple potential subjects/objects, you use "THAT/THIS". For example, say you were at an animal shelter and you wanted to take some animal home. If there only were one dog among the animals, and you liked that dog of all animals, you'd say "I like dog, I'll take it home." If there were multiple dogs, you'd point and say "I like THAT dog, I'll take it home."