What's this "we" stuff? A lot of "sola scriptura" adherents even on this forum don't abide by the same view you describe above.
I can only claim to speak for the Westminster (Reformed) view of Sola Scriptura. So when I say "we" I mean Westminster, Reformed believers. The definition of Sola Scriptura that I defend is: "The Bible alone is the Word of God and the only infallible rule of faith and practice." I think you're just diverting by claiming that there's not even a clear, agreed upon definition of Sola Scriptura. Just deal with the one I'm defending here.
So, humanly speaking, the Church wrote the New Testament and was protected from error during that process. The Church went on to compile the biblical canon and was similarly protected from error during that entire process.
But the Church won't (or can't?) be protected from error at any other time in any other context?
The New Testament was not written by "the church" in the sense that the Catholic Church publishes her dogmas. The New Testament was written by specific men, apostles, prophets, and evangelists, who were chosen by God just like the OT prophets. More than this, the NT was written by God the Holy Spirit through these men.
The church did not authoritatively compile the canon or choose the canon. The church recognized the canon and agreed with God. God chose the canon because all the canonical books are divinely inspired.
The Holy Spirit does protect the church at large and guide her into all truth. And the Holy Spirit guided the church in her recognition of the canon. But this does not mean that the church never errs. We see examples of the church erring even within the New Testament and nowhere in the NT is it taught that the church is infallible and that her judgments are as authoritative as God's written word.
And even if this
were the case (which it is not), the NT does not teach that the Roman church is the seat of this infallible authority. The church of Jesus Christ is much larger than the Roman church and a large section of Jesus' church disagrees with many of Rome's doctrines and conclusions.
Doesn't that set the bar rather low? The Holy Spirit could've clarified a few (or a lot of) sections and saved the Protestant ecclesial communities a lot of unnecessary disunity, right? Surely that would've been preferable to being in such doctrinal disagreement with each other, wouldn't it?
The Scripture is clear on the essentials and this should encourage unity. The Scripture is not entirely clear on everything and this creates room for different views and respectful disagreement. The Scripture is silent on some things and this leaves room for private judgment.
The church has no right, like the Roman church has many times done, to make authoritative statements on things that are unclear or unsaid in Scripture and bind the consciences of men to these things. Where the Bible is unclear or silent, Christians have the right to disagree with one another.