The etymological meaning of Lucifer is “bearer of light,” making Luciferians consequently the bearers of light and thus of the truth.
Also, last I checked, Protestantism has its origins in the 16th century, before which time, Christians were almost universally Catholic or Orthodox, and it is they who invented the rule that all true doctrine must come from the Bible (note that that rule isn’t anywhere in the Bible…). Talk about changing the rules, huh?
Before the Catholic church, there was no all-encompassing institution that governed the individual churches. 2 Timothy 3:16 also set the standard for living by the scriptures.
Timothy 3:16 says: “All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness[…]”
It just says it’s God-breathed and useful, which is exactly the Catholic Church’s position, and in no way even implies that it is the only acceptable source of divine truth.
I don’t think there’s much historical evidence that there was a “before the Catholic Church,” once Christianity was established. From reading the Bible and the Church Fathers, I have come across numerous references to bishops and other clergy, and even popes (from the early second century). The sacraments of baptism and communion (and confession, etc.), as described by those writers, are all consistent with Catholic teaching, sometimes even surprisingly so.