<> Challenge accepted.
I am extreme - in insisting it is The Magisterium, and not me and thee, that has the authority and when that authority takes decisions, we are bound to accept them and adhere to them. For a Catholic, this is so fundamental that it used to be a tautology.
I will provide just a few quick citations but your response surprises me because you are an obviously intelligent and very well read man.
"Satis Cognitum" by Pope Leo XIII, 1896, teaches, "They who take from Christian Doctrine what they please, lean on their own judgements, not on faith, and not "bringing into captivity every understanding unto obedience of Christ (2 Cor. 10-15), they more truely obey themselves than God."
Catechism #892 "Divine assistance is also given to the succesors of the apostles, teaching in communion with the succesor of Peter, and , in a particular way, to the Bishop of Rome, pastor of the whole Church, when, without arriving at an infallible definition and without pronouncing in a "definitive manner, they propose in the exercise of the ordinary Magisterium a teaching that leads to bettter understanding of Revelation in matters of faith and morals. To this ordinary teaching the faithful "are to adhere to it with religious assent" which, though distinct from the assent of faith, is nonetheless an extension of it."
"Taking conciliar custom into consideration.." there can be no other reponse than for individual Christians to accept the decisions of an Infallible Ecumenical Council and all Ecumenical Councils are infallible. What you cite is a protestant principle and it inverts right reason and reality and there is nothing traditional or customary about it.<>