Caveat: I was told this by a Greek Orthodox friend on why the Greek Orthodox Church is the one true church. I'll leave it to others to shoot down or support.
That doesn't quite cut it with doctrinal credence. The first Apostles healed and performed miracles. The Catholic "miracles" they base "sainthood" on is suspect as well. It is best to be Sola Scriptura so that God doesn't ask questions we can't answer.
As with "unanimous consent of the fathers , "unbroken" is defined as allowing for no popes for years or even rival popes, while preservation even means the kind of church that RCs condemn many Prots for basically holding Rome became, necessitating the Reformation, while the deformation was actually deeper.
Cardinal Ratzinger observed,
"For nearly half a century, the Church was split into two or three obediences that excommunicated one another, so that every Catholic lived under excommunication by one pope or another, and, in the last analysis, no one could say with certainty which of the contenders had right on his side. The Church no longer offered certainty of salvation; she had become questionable in her whole objective form--the true Church, the true pledge of salvation, had to be sought outside the institution. It is against this background of a profoundly shaken ecclesial consciousness that we are to understand that Luther, in the conflict between his search for salvation and the tradition of the Church, ultimately came to experience the Church, not as the guarantor, but as the adversary of salvation. (Joseph Cardinal Ratzinger, head of the Sacred Congregation of the Doctrine of the Faith for the Church of Rome, “Principles of Catholic Theology,” trans. by Sister Mary Frances McCarthy, S.N.D. (San Francisco: Ignatius, 1989) p.196). http://www.whitehorseinn.org/blog/2012/06/13/whos-in-charge-here-the-illusions-of-church-infallibility/)
• Joseph Lortz, German Roman Catholic theologian:
“The real significance of the Western Schism rests in the fact that for decades there was an almost universal uncertainty about where the true pope and the true Church were to be found. For several decades, both popes had excommunicated each other and his followers; thus all Christendom found itself under sentence of excommunication by at least one of the contenders. Both popes referred to their rival claimant as the Antichrist, and to the Masses celebrated by them as idolatry. It seemed impossible to do anything about this scandalous situation, despite sharp protests from all sides, and despite the radical impossibility of having two valid popes at the same time. Time and time again, the petty selfishness of the contenders blocked any solution...”
Cardinal Bellarmine:
"Some years before the rise of the Lutheran and Calvinistic heresy, according to the testimony of those who were then alive, there was almost an entire abandonment of equity in ecclesiastical judgments; in morals, no discipline; in sacred literature, no erudition; in divine things, no reverence; religion was almost extinct. (Concio XXVIII. Opp. Vi. 296- Colon 1617, in “A History of the Articles of Religion,” by Charles Hardwick, Cp. 1, p. 10,)
• Erasmus, in his new edition of the “Enchiridion: “What man of real piety does not perceive with sighs that this is far the most corrupt of all ages? When did iniquity abound with more licentiousness? When was charity so cold?” (“The Evolution of the English Bible: A Historical Sketch of the Successive,” p. 132 by Henry William Hamilton-Hoare)
• Catholic historian Paul Johnson additionally described the existing social situation among the clergy at the time of the Reformation:
“Probably as many as half the men in orders had ‘wives’ and families. Behind all the New Learning and the theological debates, clerical celibacy was, in its own way, the biggest single issue at the Reformation. It was a great social problem and, other factors being equal, it tended to tip the balance in favour of reform. As a rule, the only hope for a child of a priest was to go into the Church himself, thus unwillingly or with no great enthusiasm, taking vows which he might subsequently regret: the evil tended to perpetuate itself.” (History of Christianity, pgs 269-270)
• In the summer of 1536, Pope Paul III appointed Cardinals Contarini and Cafara and a commission to study church Reform. The report of this commission, the Consilium de emendanda ecclesiae, was completed in March 1537. The final paragraphs deal with the corruptions of Renaissance Rome itself:
“the swarm of sordid and ignorant priests in the city, the harlots who are followed around by clerics and by the noble members of the cardinals’ households …”
“The immediate effects of the Consilium fell far below the hopes of its authors and its very frankness hampered its public use. … the more noticeably pious prelates [note: this the “noticeably pious” clergy] had no longer to tolerate the open cynicism of the Medicean period, and when moral lapses by clerics came to light, pains were now taken to hush them up as matters of grievous scandal.” (G. Dickens, “The Counter Reformation,” pp. 100,102)
In the same candid spirit is the following statement of de Mézeray, the historiographer of France: [Abrege’ Chronol. VIII. 691, seqq. a Paris, 1681]
“As the heads of the Church paid no regard to the maintenance of discipline, the vices and excesses of the ecclesiastics grew up to the highest pitch, and were so public and universally exposed as to excite against them the hatred and contempt of the people. We cannot repeat without a blush the usury, the avarice, the gluttony, the universal dissoluteness of the priests of this period, the licence and debauchery of the monks, the pride and extravagance of the prelates, and the shameful indolence, ignorance and superstition pervading the whole body .... These were not, I confess, new scandals: I should rather say that the barbarism and ignorance of preceding centuries, in some sort, concealed such vices; but,, on the subsequent revival of the light of learning, the spots which I have pointed out became more manifest, and as the unlearned who were corrupt could not endure the light through the pain which it caused to their eyes, so neither did the learned spare them, turning them to ridicule and delighting to expose their turpitude and to decry their superstitions.”
Bossuet* in the opening statements of his “Histoire des Variations,” admits the frightful corruptions of the Church for centuries before the Reformation; and he has been followed in our own times by Frederic von Schlegel [Philosophy of History, 400, 401, 410, Engl. Transl. 1847.] and Möhler. [Symbolik, II. 31, 32, Engl. Transl.]