You are certainly bringing out the problems with it. The position I am familiar with is that the only authoritative interpreter of Scripture is its Author - the Holy Spirit.
But who makes the authoritative ruling that an interpretation truly was done by the Holy Spirit versus another spirit?
Again, this comes down to another magisterium. And this magisterium is NOT the Holy Spirit.
Where there are contradictory interpretations between two SSers, ideally they would go in prayer and ask God to show them who is right and who wrong.
Which according to this standard of yours, is not being done, as we have tens of thousands of denominations (including millions of “Churches of One”) all claiming their interpretation is truly guided by the Holy Spirit.
The Holy Spirit does not contradict Himself. He is God. Thus all of these interpretations cannot be true.
The only interpretation of scripture that is true is the one held by Christ and the Twelve Apostles.
Introducing the Holy Spirit as the magisterium resolves the problem with the lack of one.
Actually it doesn’t.
Who made the authoritative ruling that one’s interpretation truly is guided by the Holy Spirit?
And if an interpretation truly was done by the Holy Spirit, it would have been written down in the Bible (sola scriptura) or else it would be an extra biblical tradition, which is a violation of sola scriptura. And since this tradition would come from the Holy Spirit, it would be Sacred Tradition.
We Catholics believe in Sacred Tradition. Sola scripturists are not supposed to. But here they are defending a form of sacred tradition, while claiming to hold to sola scriptura.
Catholics in contrast can be indicted for taking their theology seriously concerning the church being the body of Christ.
Which is in the Bible or is Ephesians 5 a decoration?
SS, as I noted above, has as much to do with ecclesiology as with authority. Regardless of which definition of SS is used, one thing is clear: the ultimate authority under it is not the church but the Lord. Catholics will agree with that, but will insist on a much higher role for the mediation of the church in interpretation than Protestants are willing for it to bear.
But that’s the thing: Under sola scriptura, a magisterium or traditions are not allowed, yet protestants accept their interpretation of scripture (tradition) and the magisterium that declares their interpretation of scripture is truly by the Holy Spirit as authoritative.
We Catholics admit we hold to a theological tripod. Sola scripturists hold to a theological tripod too, but refuse to admit it.