If the Constitution were truly immutable, different iterations of the Supreme Court wouldn't be able to interpret the same words in different ways. In fact, we wouldn't even need a Supreme Court to interpret it. It would always mean exactly what it says in no uncertain terms, with the absolute certainty of mathematical proof.

But it is edited through the interpretation of the Supreme Court. And that's by design - the Constitution was written to be intentionally vague, which makes it unavoidably mutable.