The problem is not admitting that "Orthodox Christianity" was manifestly not Orthodox as regards the NT church, as shown, and that thus the Reformation itself, though it basically corrected the salvific error of Rome, that of justification by one's own holiness thru sprinkling of water, and purgatory (usually), must be continued.
It seems to me, to embrace that position, one must then abandon almost 18 centuries of historical Christianity, admitting there was no visible orthodox church, and all of the visible churches were erroneous (except you take the position of Independent Findamental Baptitsts, in which case 99.9% or so of the world was lost all those centuries, and even now). Evolving or Emergent Protestantism reminds me somewhat of the modern biblical translations. They keep improving. I think this is the Revelation, or perhaps Preterist position, that the Gentiles were left to their own devices after the last apostle passed and the Jews and Gentiles of the first generations were martyred and failed to appoint orthodox successors. This view seems seems incongruent with 17 And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven. 18 And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it. 19 And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.
I think the Moslems argue that the Jews and Gentiles failed and made it necessary for another prophet, albeit not Martin Luther, to arise afterward to lead people out of darkness. I think the Mormons have a view like this, although with different prophets. It seems to me that one ring that binds them all is to try to destroy the Catholic Church. That may seem oddly recognizable if one is not attached to one of the warring parties.