Your repeated use of the word "cannot" is merely a Straw Man Fallacy on your part. The simple fact is that God has chosen to do things a certain way---after all, as you admit, "God can endow who he wills," right? And he wills to endow the bishops (Magisterium)---and not laymen like you and I---with his own power and authority. God's choice, whether it fits your high opinion of yourself or not.
Just another expression of your prior Straw Man Fallacy (see above).
Why---because they say so? No, only those who have been ordained and appointed by Christ's one historic Church (i.e., the Magisterium) can rightly consider themselves endowed with Christ's own ecclesial authority. That's just the way in which God has chosen to govern his Church. Sorry if this pokes a few holes in your self-styled religious identity.
Like yourself, I have no idea what you're talking about here. Example?
Correction of individuals comes by means of the bishops of Christ's one historic Church, just as it came through the apostles (i.e., the original Magisterium) in the 1st century.
Luther was not a bishop of Christ's Church, and thus possessed absolutely no divine authority whatsoever to try and replace the Church's established teachings with his own entirely non-authoritative interpretations and opinions. Your example here only serves to prove my point.
Gaudium de veritate,
Cruciform
+T+