While Lutherans would affirm that the office of the public ministry (for us the pastoral office) is a necessary element for Christ's Church, having or not having a pope is another matter entirely. It might be that a papacy by agreement and not by divine right would be beneficial but it could be that such a papacy would be harmful. One might go no further than the current Pope to illustrate the point. It is becoming harder and harder for the stalwart Roman Catholics to abide this Pope and more difficult than ever to put up with his inconsistencies, his autocratic rule, his tendency to blame everyone but himself, and his failure to communicate anything bordering on cohesive for the church he leads.
As a Lutheran, this is not my problem but does affect me and all Lutherans. Rome is the elephant in the Christian room and when Rome stumbles we all end up with a bit of a bloody nose. Yet this Pope essentially gives the reason why we Lutherans do not have one. When popes are good, things are great and when popes are bad, things are terrible. So much is deposited upon the weight of this one man and this one office.
As Lutherans we have our own problems. Someone has quipped that Lutherans don't have one pope, they have thousands. To our harm, just as every parish delights in operating on its own except when it needs something a synod or national or regional jurisdiction can offer, so do our pastors delight in being independent in less than helpful ways to the cause of the Church as a whole. If for this reason only it would be nice to have a pope who could tell those on the fringes of Lutheran faith and practice to move into the mainstream of our confession and liturgy or depart from us. But Rome has a pope and it seems almost impossible for this or any pope to rein in the extremes in Rome. If the essence of the Petrine ministry is unity of faith and practice, then I am not sure this ministry is working, or if it is, if it is worth anything. Now to be sure, I am confident that Roman Catholics would insist that there is much more to the Petrine Ministry than this, but this is perhaps the most urgently need sign and neither Benedict nor Francis have made much headway on this. In fact, not even John Paul II for all his tenure in the office did.
The result of our independent ways is that the world is often simply confused. What does it mean to be Christian? What is the Church and why is she? Christianity as a whole has no clear answer to these questions and even within the individual jurisdictions, there is little unanimity. It is not because the Scriptures are a muddle or the Gospel is veiled. Christ is the center of God's Word -- its speaker and the One of whom it speaks. The Gospel is defined over and over again by our Lord. That the Christ must be betrayed into the hands of sinners, suffer, die on the cross and on the third day rise. So God is not our problem we are -- a problem not even a Petrine ministry and a pope can fix. So for a Lutheran who sighs at the ambiguities within his tradition, who looks upon the shallow and broad river that is Protestantism, and who sees the same mess in Rome but magnified by its size, there is little confidence in the Petrine Ministry -- especially when the one who exercises that ministry now is himself a big part of the problem.