Language isn’t an exact science. Often, there is no "perfect" answer.
While much is logical, many elements are harder to explain, untethered as they are to any fixed set of rules. For instance, when is a thought expressed with an indicative vs a subjunctive mood? When to use polite vs casual phrasing in languages such as Korean or Japanese? How to articulate an expression that doesn’t exist in a target language?
We often take language for granted. Many people claim they “perfectly” speak their mother tongue. But who defines “perfection”?