My thinking too. If there were ten people on the island, and you gave each a Bible, you'd have at least ten different interpretations.
Which is why we don't hand someone a Bible without guidance and have them figure it all out on their own.
I would agree that the Bible by itself doesn't; but when we say "Scripture Alone" we (at least those of us who affirm the theology and teachings of the Reformation) don't mean some sort of "Bible Onlyism". We mean Scripture alone is the Norming Word, which norms and regulates true Christian teaching and faith; for whatever is contrary to Scripture is contrary to the faith.
But we don't hand people a Bible and tell them to figure it out, the Bible is read within the Communion of Saints, within the fellowship of the Una Sancta; the one holy, catholic, and apostolic Church.
-CryptoLutheran