The authority of the Extraordinary Magisterium is not just my own opinion. Some of the thoughts I expressed about the logical implications of denying this authority are my own original reflections, but these only speak to my personal motivations for defending ecclesial authority; they don’t mean that authority itself is just a matter of my own opinion.
Consider, for example, the Dogmatic Constitution
Pastor aeternus of the First Vatican Council:
ewtn.com/faith/teachings/papae1.htm
(this is an abridged version).
Consider also the Dogmatic Constitution on the Church
Lumen Gentium of the Second Vatican Council:
vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_const_19641121_lumen-gentium_en.html
Look especially at Chapter III there.
I could pull excerpts from these (I began to), but they would be long excerpts and I don’t want to violate CAF rules about long posts consisting mostly of quotes. I could go on finding further sources but do you really think the Church hasn’t taught on the subject of the structure and authority of the college of bishops?