|The ordinary Ordinary|
I would also like to expand upon J.'s adumbration of the lines from Pastor Aeternus about "ordinary jurisdiction." This does not mean papal rule over a diocese is in any way to be considered normal. What is does mean is that when the pope intervenes in a diocese, he possesses the same power as the local ordinary bishop. An "ordinary" is the cleric in charge of a community, not necessarily even a bishop. Msgr. Keither Newton is just a priest and presides over the Ordinariate of Our Lady of Walsingham (please do not call it the "Anglican Ordinariate"). The same is true of Msgr. Steenson in America. In large dioceses and archdioceses, there are often multiple bishops, the ordinary and the auxiliaries—whose function is sacramental. The pope has the same power as the local ordinary when he exercises it, but the ordinary rule of a diocese belongs to the ordinary. Get it?
It seems that in both cases of papal intervention and in exercises of ex cathedra teaching, the pope is bound by prudence and respect for the bishops of the rest of the church who possess ordinary ruling and teaching power in their local churches. Were a Roman dicastry to begin issuing directives, programs, daily schedules, and making decisions for each diocese in the world, the pope would be abusing his power severely. Similarly, infallibility must know limits beyond the conditions laid down in Pastor Aeternus. Were the pope to define that 2+3 equals 5, he would do so infallibly, but pointlessly. I for one always wondered what the point was behind Pius XII's non-definition of the Assumption of Our Lady, given that the Assumption was never disputed within the Church. The sinlessness and the conception of Our Lady were in question for quite some time until a lid was put on it during the Renaissance and Pius IX closed the issue definitively.
It may all be a moot point now. The Roman part of the Catholic Church is in a malaise created, in part, by a wild papacy, but that is no longer the problem. Bad bishops and an overgrown bureaucracy reign now. The pope is a luminary and high profile figure, but less of an active figure in Vatican activities than say Pius XII or Pius X. One could say that the Church was once like a great orchestra, wherein all the talented players were obscured by a strong willed conductor. Now we are more like a rock band: big name, high publicity players mismanaged by an ever growing machine, each gear looking to get greased.