That “institution” is the Holy Roman Catholic Church. Institued by Christ to lead his flock to all Truth through the power of the Holy Spirit.
For 2,000 years The Catholic Church has been preserved from error on orders from God and exists to this day to preach and teach those here now and the generations to come.
There is no bible for you to critique the Church without the Church. And because The Church is part of the Body of Christ it reflects Christ’s mercy for the salvation of the ignorant. Even when the protestant does not. One can be assured of the true Church by that alone. Who cares for those who through no fault of their own do not know Christ? The Catholic Church does.
God desires everyone to come to Him and to realize the fullness of Truth. The Truth is not to be found amongst the myriad of individual scriptural interpretation.
P.S. those “extras” you refer are the Body and Blood of Christ in the Eucharist. Not something I would dismiss lightly.
Pope Stephen VI (896–897), who had his predecessor Pope Formosus exhumed, tried, de-fingered, briefly reburied, and thrown in the Tiber.[1]
Pope John XII (955–964), who gave land to a mistress, murdered several people, and was killed by a man who caught him in bed with his wife.
Pope Benedict IX (1032–1044, 1045, 1047–1048), who "sold" the Papacy
Pope Boniface VIII (1294–1303), who is lampooned in Dante's Divine Comedy
Pope Urban VI (1378–1389), who complained that he did not hear enough screaming when Cardinals who had conspired against him were tortured.[2]
Pope Alexander VI (1492–1503), a Borgia, who was guilty of nepotism and whose unattended corpse swelled until it could barely fit in a coffin.[3]
Pope Leo X (1513–1521), a spendthrift member of the Medici family who once spent 1/7 of his predecessors' reserves on a single ceremony[4]
Pope Clement VII (1523–1534), also a Medici, whose power-politicking with France, Spain, and Germany got Rome sacked.