First, let me say that I am not only a premillennialist, my eschatology is pretty much standard fundamentalist Baptist stuff which means I see a real possibility of connection between the Church of Rome today and the future world government/church of the Revelation. That might be in the "less-than-dogmatic" column, however.
What's more clear is history. There was a Reformation. Certain dramatic changes transpired as Protestant churches were born out of the move to correct Rome's perversion of Biblical teachings.
Another thing clear, to me at least, is that the Reformation was not complete nor perfect. Many (most?) of those Protestant churches did more to correct doctrinal error than other aspects of Romanism, like liturgy, iconography, other trappings which were to some degree or another carried into the "new" churches.
One would have hoped, had he lived in the 16th century, to see the purification of doctrine continue through the years, getting purer and purer as time went on. I don't think this happened either. It peaked somewhere. Someone with a better grasp of church history might be able to pinpoint a date.....my guess is that the peak of "improvement" was long before 1840......maybe in the mid-1700's.
Since that peak, whenever it occurred, the doctrinal stance of the Protestant churches in general has been on a downhill slide. Consider a few factors: mid-19th century: Finney-ism begins, the German Biblical "higher criticism" begins; early 20th century, American "modernism" begins, led by the Fosdicks and Van Dykes among others. By the mid-20th century, we have the new permutation of Finney-ism promoted by the "fundamentalists" so-called, the decisional regeneration movement from Billy Graham to Jack Hyles.
A reaction to that superficial theology of the late 20th century gave birth to a resurgence of calvinist soteriology, especially in the Baptist world. The idea that God is truly sovereign regained a place of prominence in some circles. From 1990 or so, we have been taught and led by men like Al Mohler, John Piper, John MacArthur, and many others, and this has led to to a renewed appreciation of Martyn Lloyd-Jones, A. W. Pink, the Puritans, and other sources of solid Biblical teaching from the past.
I think another peak has been reached and passed, however, and will elaborate on that thought in Part Two.