The Magisterium is much more than that. It is the teaching authority of the Church. It consists of all of the bishops of the Church including the bishop of Rome (Pope) and to a large degree all of their predecessors. They are collectively acting under the direct authority of Jesus Christ who promised to protect the teaching of the Church:
"He who hears you, hears me; he who rejects your rejects me, he who rejects me, rejects Him who sent me" (Luke 10:16)
They are under the guidance of the Holy Spirit through Apostolic Succession. Remember no bishop exists, or has ever existed who has not had the hands of a bishop placed upon him during ordination. This is a direct line directly to the original Apostles.
God did not take them lightly, they do not take themselves or their duties lightly, and I shall not take them lightly either.
Grace 101. "Study to shew thyself approved unto God, a workman who needeth not to be ashamed, rightly dividing the word of truth." 2 Tim. 2:15.
Music to those of us who believe that God has given EVERY BELIEVER the ability to study His word of truth. Through the Holy Spirit, residing in each believer. We don't need to give our God-given abilities to understand His word to anyone else.
Prove it.
But you do admit that scoundrels, at times, were allowed into the fold, don't you? That wolves, disguised as sheep, were allowed into the very seat of Peter, yes? That this "infallible" Magesterium was able to be bought off, blackmailed, scandalized and found to be heretics, as well, do you not? Seeing as the history of the Magesterium is not as stellar as I'm sure everyone would desire them to be, is it not then understandable, even expedient, that each Christian be allowed to study the Holy Scriptures and enjoy that same leading and guiding of the Holy Spirit that indwells every true child of God that cannot be exclusively claimed by others simply based upon their status in the Church? Why would the Holy Spirit guide those seeking truth from God's word differently than he would "officials" of the church? I ask these questions not to trick or harass but simply to challenge the lock-step thinking that has allowed error to slip into Christian doctrine.