I don’t think the church petered out, or shrunk in authority, I simply don’t think the church is what Catholics think it is. They seem to think that it is an earthly organization that was founded by Christ through Peter, whereas I think it is a spiritual organization founded by Christ through the Holy Spirit. I know that Catholics at least acknowledge the spiritual church, but they act as if the earthly one has more importance, when just the opposite is true: the earthly church is just a shadow of the heavenly body of all believers.
How does a purely invisible church adjudicate between two earthly people who have a dispute?
And at times in history, there have been really big disputes about really big things, such as: what is the list of books which we must regard as the Bible (Sacred Scripture)? How, when and where did an invisible church give a binding ruling on that?
I repeat: how, when, and where?