But Scripture does say it's sufficient.
2 Timothy 3:14-17 But as for you, continue in what you have learned and have firmly believed, knowing from whom you learned it and how from childhood you have been acquainted with the sacred writings, which are able to make you wise for salvation through faith in Christ Jesus. All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work.
If Scripture were insufficient then it couldn't make the man of God complete, nor equipped for EVERY good work.
2 Timothy 3:14-17
If Scripture were insufficient then it couldn't make the man of God complete, nor equipped for EVERY good work.
Scripture is certainly profitable and useful (from the Greek ophelimos) for teaching, but that doesn't make it mandatory or sufficient for teaching every individual point of theology, and not at all without Tradition (2 Thess 2:15). There are far too many seriously misguided and contradictory Christian sects in history and even today to believe that Scripture alone is sufficient.
Also, many of the Epistles weren't yet written and none of the New Testament books were in the Canon of Sacred Books when St. Paul wrote this. Much less when Timothy would have been a child. To take these verses as a justification for Sola Scriptura would mean that only the Old Testament was binding and that the New Testament wasn't necessary at all.