It's also significant that a number of the "modern" revisions of doctrine have their roots in early heresies that were specifically condemned. Surely the increase in liberal theology is one of the signs we're in some stage of the End Times.
The Orthodox make the valid point that the supposed
sola scriptura of Protestantism has resulted in thousands, if not tens of thousands, of competing understandings of Scripture. Sola scriptura ends up really being "my understanding of Scripture" versus "your understanding of Scripture" versus "their understanding of Scripture."
There is a branch of Protestantism called "paleo-orthodoxy" that, like Orthodoxy, focuses primarily on the Apostolic and Early Church Fathers as well as Scripture. Thomas C. Oden was one of the leading exponents. His
Classic Christianity is one of the better systematic theologies I have found:
Classic Christianity: A Systematic Theology: Oden, Thomas C.: 9780061449710: Amazon.com: Books.