Walter 'Anglican Patrimony' Frere, an Anglican monk, bishop, historian, theologian, liturgical scholar, a participant in the Malines Conversations about Unity between Rome and the Church of England, wrote about the context in which S Theodore deemed that S Chad's Consecration was null. "In ancient days ... the Church, before accepting [a man] as a bishop, wisely asked, not merely whether the consecration had been done by bishops, but whether it had been done by the church, and the real church, and with real church sanctions, and without moral or canonical lets or hindrances, such as simony and the like. And unless it was satisfied on such points, it treated the orders given as null. The result of this policy in an age of faction and of great moral disorder was, no doubt, to throw ordinations into a complete chaos. The state of the Roman ordinations in the ninth century is a classical instance of this; and probably it was in consequence of this ... that the Church began to take a more mechanical view, and to extol the machinery ...".
Frere was not actually talking about S Chad. He probably had in mind such pontificates as that of Stephen VII, who exhumed the decaying corpse of his predecessor Formosus, propped it up and put it on trial (I'm afraid a conviction followed) and then declared null all of Formosus' ordinations. (Yes, a striking exercise of the Petrine Magisterium!) Formosus' crime had been to allow himself, when already a Bishop, to be translated to Rome.
I think we need to understand this sort of background so as to understand that when passions are roused, 'mechanical' concepts of sacramental validity tend to give way to ... er ... Common Sense, with all its sad inaccuracies and inconsistencies. In one of the longest persecutions in the Church's history, we Anglicans connived in a bloodthirsty system in which young men, trained to bring the ancient form of the Sacraments back to a country in which (any form of ) the Eucharist had practically ceased to exist, were put on trial for 'priesthood' and cruelly done to death. It is hardly surprising that when eventually we, the persecutors of 'the priests', suddenly decided to tell everybody that, actually, we also were 'sacrificing priests' ourselves, the assertion was not welcomed with open hearts.
I do not see how we can expect not to have to live with the consequences of our history. That is the deep-down reason why the current juridical dispositions of the Catholic Church lay this burden of 'reordination' upon us.