Nobody is ignoring it. In the normal course of events it is absolutely true. However, it assumes something not currently in evidence; that the Roman Pontiff is in conformity with his predecessors and Church Tradition. For instance, there is currently a school of thought (among several others) that says that Francis is not the true Roman Pontiff.
As I said, "uncharted waters".......
It certainly seems modern Catholics are doing what Luther did....questioning the teaching of the RCC.
And just who gets to decide whether or not he is the true pope?
Did not your college of cardinals elect him?
Are they led by the Holy Spirit in the selection of the pope or not?
Where does any of the laity get off deciding whether the CoC and the pope are legit or not? ON what authority are they given this right?