Gnosticism does not have to be that complex ,my friend. As New Advent points out...
Gnostics were "people who knew", and their knowledge at once constituted them a superior class of beings, whose present and future status was essentially different from that of those who, for whatever reason, did not know.
This is what Martin Luther did when He invented solo-scriptura,thus Luther became gnostic in that particular belief that allows for many to fall into error
Nor do Protestants think we’re “given some special individual revelation of scripture never seen before”
Ask yourself why you do not have single unity in protestant communities with agreed upon dogmatic teachings on faith and morals to be obedient to?
The reason you don't have them is because separated communities have there own "special revelation" of what faith and morals is. It's a "do it my way" theology
I saw this first hand being in the Methodist Church for almost 20 years before converting back to Catholicism
First, gnostics were NOT just people who knew something special that made their present and future state different from someone who did not know. If that were true, then ALL Christians must be gnostics, since we know something that saves us in this life and the next!
Luther didn’t invent sola scriptura. The early church knew and practiced it, which is why scripture was cited to refute heretics and justify theology. The early councils were concerned with making theology align with scripture.
Indeed, that is why they were forced to deal with canon - so they would know what was reliable for doctrine.
Rome rejected sola scriptura, since it left no way for the Bishop of Rome to become ‘Vicar of Christ’.
There are ample ‘Protestant’ denominations that reject sola scriptura, which is why we have Lutherans promoting homosexuality. You cannot find a liberal protestant church that ACCEPTS sola scriptura!
Among those that accept it, the doctrinal divisions are few. Free Will vs Predestination. Allow infant baptism, or not. Perhaps debate about speaking in tongues.
Beyond that, I can’t think of much.