The problem for your claim of "doctrinal drift," PM, is that there is far more doctrinal drift evident among the churches that claim to follow sola scriptura than there is among those who claim to follow scripture plus tradition.
We've been separated from the Armenians and the Copts since the council of Chalcedon (AD 451), yet we are in closer doctrinal agreement with them than the Missouri Synod Lutherans are with the Southern Baptists -- not to mention that we are in closer agreement with the Armenians and Copts than we are with the Southern Baptists.
We don't claim that the writings of the Fathers are on par with Scripture. Scripture is inspired. Even the most authoritative patristic documents (e.g., the dogmatic decrees of the ecumenical councils) aren't inspired, only infallible. ("Inspiration" is the positive protection that guarantees that a document says exactly what God wishes it to say; "infallibility" is a much weaker negative protection that guarantees that a document will not say what God cannot permit it say.)
But if you use tradition to bind your understanding of Scripture to "what is believed everywhere, at all times, by everyone" (St. Vincent of Lerins) -- that is, you make sure that you're understanding the Bible in a way that is compatible with the way the Church has understood it in the past -- you are actually insuring yourself against doctrinal drift.
Ironically, part of what Luther did was to rediscover authentic Catholic tradition that had become obscured, not in the official teaching of the Church, but in the popular piety of the Catholics of his day. Unfortunately, he didn't stop there. If he had, we might today call him St. Martin of Wittenberg, Priest and Doctor.
Coulda, woulda, shoulda. We could play those games too.
If Pope Leo X and Cardinal Cajetan hadn't excommunicated Luther, but recognized his 95 theses raised some valid objections, there wouldn't have been a Lutheran schism.
It's water under the bridge. What matters today is what you recongized - that Luther rediscovered what had been obscured, as you rightly observed, by the popular piety of the Catholic church.