If questioning a pope's prudential judgments was schismatic, as it supposedly was for Fr. Vaughn Treco, then St. Paul would have been excommunicated.
Saint Peter, or Cephas as he was called, was given a vision as recorded in chapter 10 of the Acts of the Apostles that the keeping of the Mosaic law was no longer required by God. This he taught infallibly at the Council of Jerusalem as recorded in chapter 15 of Acts.
But when he went to Antioch, he ate with the so-called Judaizers who taught that Christians must keep the Mosaic law and receive circumcision. This is when St. Paul criticized the prudential judgment of a reigning pope as he saw that St. Peter's act would scandalize other Christians into thinking they too must keep the Mosaic law. The incident is recounted by St. Paul in Galatians 2:11–14 as follows:
But when Cephas was come to Antioch, I withstood him to the face, because he was to be blamed. For before that some came from James, he did eat with the Gentiles: but when they were come, he withdrew and separated himself, fearing them who were of the circumcision. And to his dissimulation the rest of the Jews consented, so that Barnabas also was led by them into that dissimulation. But when I saw that they walked not uprightly unto the truth of the gospel, I said to Cephas before them all: If thou, being a Jew, livest after the manner of the Gentiles, and not as the Jews do, how dost thou compel the Gentiles to live as do the Jews?
A pope's prudential judgments, such as allowing Communion in the hand or not disciplining heretical clerics, are certainly not infallible and can be questioned by the faithful.
Father Treco questioned certain prudential judgments of recent popes and was excommunicated for doing so. He was most critical of papal inactivity, however, such as Pope St. Paul VI's decision to not correct known heretics and the decision by Pope Francis to not stop Holy Communion from being received sacrilegiously by Catholics living in sin.
The Catholic Church teaches Her popes are not impeccable, meaning they can commit sins of commission and of omission. Popes sin and go to confession. The Church also teaches that popes are infallible, meaning unable to error in teaching, only when they teach Catholic faith and morals in a definitive way to the universal Church.
Catholics may even disagree with popes on certain prudential judgments that touch the application of doctrine such as when to apply the death penalty in various societies. Cardinal Joseph Ratzinger in 2004 as head of the Congregation for the Doctrine of the Faith makes this very point:
If a Catholic were to be at odds with the Holy Father on the application of capital punishment or on the decision to wage war, he would not for that reason be considered unworthy to present himself to receive Holy Communion. ... There may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty.
Watch the panel discuss the excommunication of Fr. Treco in The Download—Inciting Schism.