Many of the responses to the OP center around the concept that somehow one particular branch of Christianity has maintained constant rules for worship or government and is thus a more pure version off what the NT envisions the church should be.
The problem is of course had the 16th century reformers seen a reflection of NT practices in any of the non-Roman Orthodox churches then it is likely that most modern protestant groups would look a lot like Orthodox churches. But they don't, rather the product of the early reformation looks more like Rome than Orthodox.
Here is the best response:
Irenaeus wrote his Against Heresies probably around AD 180. Irenaeus himself introduced error but say 150 years after Christ,,, lots of error.
If you look at Revelation ch 2&3 there is enough error to warrant comment. If you place that book at AD 95 or so that would be 90 years before Irenaeus. Paul corrects error in the churches at an even earlier time. My personal opinion is that the organic church suffered from Gnostic and other like influences at a very early time, probably even before the Apostles had all died. But there wasn't enough popular outrage until the 16th century to cause a revolt.
Further to that my opinion is that the reformation fixed some wrongs but didn't go far enough as much of the protestant groups today still practice a salvation that requires at least some works. Most likely reform will be needed on a continual basis until the Lord returns.
