While what you state here may be what is practiced by some, it is not the intent of sola scriptura. The intent of sola scriptura is most importantly a practice of the Church, used for hermuenetics.
The Lutheran confessions declare:
We believe, teach, and confess that the sole rule and standard according to which all dogmas together with [all] teachers should be estimated and judged are the prophetic and apostolic Scriptures of the Old and of the New Testament alone, as it is written Ps. 119:105: Thy Word is a lamp unto my feet and a light unto my path. And St. Paul: Though an angel from heaven preach any other gospel unto you, let him be accursed, Gal. 1:8.
OK, I see what you’re saying. I think you’re pointing out that “sola Scriptura” does not necessarily have to mean what it often comes to mean; and in addition, you’re pointing out that Lutheran tradition is much nearer to Catholic tradition on this point than to, say, the Baptist tradition I grew up in. For what it’s worth, most of the Baptists, Presbyterians, Independent Evangelicals, and similar conservative evangelicals I grew up around would probably agree (then say the Lutherans were wrong. heh). So there’s not a lot for us to disagree about.
The only thing I think you may be missing is how strong the fracturing tendency of “sola Scriptura” as a Reformation slogan has been. Luther, of course, is not directly responsible for the articulation of “sola Scriptura” as we know it. I’ve usually seen it traced through a line from Melancthon (with his argument that Biblical authority was the “formal cause” of Reformation) through Calvin (with the WCF as the most-copied articulation of the Reformed doctrine of Scripture).
Again, I like to emphasize over against the Catholic tendency of lay neglect of Scripture the teachings of Augustine and others regarding the centrality of Biblical authority in the Tradition, as
ccel.org/ccel/augustine/doctrine.x_1.html .
The question I think you have to ask yourself about “sola Scriptura” is whether you can consistently articulate “the Bible read within the Church” in a way that
justifies schism from the unity of the Catholic faith, but
doesn’t justify “every man hath a song, every man a doctrine.” Historically, it has not happened that way; Protestantism remains divided between “mainline” or “confessing” traditions which emphasize their redefinition of “church” but claim “sola Scriptura” over against the Catholic Church, and the endlessly fragmenting “evangelical” or “fundamentalist” or “neo-Reformed” traditions which emphasize “sola Scriptura” in a way which arrives at the “private judgment” problem I was addressing. I came to the conclusion that I could not have it both ways, which is one reason I came Home.
Check out Louis Bouyer,
Spirit and Forms of Protestantism, if you haven’t already.