I did not think that it was Catholic doctrine that the Church could not err about anything but, rather, that it could not err regarding faith and morals. If my understanding is wrong, and Catholics believe that the Church simply cannot err about anything at all in the realm of existence, please let me know.
Assuming that my understanding is correct, then why can’t the Church admit error in conducting the Inquisition? It is not like the Church is admitting error in finding that certain people were heretics, or that these people’s beliefs were heretical, but instead that the Church should not be in the business of using torture and other coercive techniques to determine and ensure conformity with Catholic beliefs. Again, the issue is not the truth of those beliefs but the actions of the Church in enforcing the faith.
en.wikipedia.org/wiki/Pope_John_Paul_II#Apologies
Apologies
Over the later parts of his reign, John Paul II made several apologies to various peoples that had been wronged by the Catholic Church through the years. Even before he became the Pope, he was a prominent supporter of initiatives like the Letter of Reconciliation of the Polish Bishops to the German Bishops from 1965. During his reign as a Pope, he publicly made apologies for over 100 of these wrongdoings, including:
The persecution of the Italian scientist and philosopher Galileo Galilei in the trial in 1633 (October 31, 1992).
Catholic involvement with the African slave trade (August 9, 1993).
The Church Hierarchy’s role in burnings at the stake and the religious wars that followed the Protestant Reformation (May 1995, in the Czech Republic).
The injustices committed against women in the name of Christ, the violation of women’s rights and for the historical denigration of women (July 10, 1995, in a letter to “every woman”).
Inactivity and silence of some Roman Catholics during the Holocaust (March 16, 1998).
For the execution of Jan Hus in 1415 (December 18, 1999 in Prague). When John Paul II visited Prague in 1990s, he requested experts in this matter "to define with greater clarity the position held by Jan Hus among the Church’s reformers, and acknowledged that “independently of the theological convictions he defended, Hus cannot be denied integrity in his personal life and commitment to the nation’s moral education.” It was another step in building a bridge between Catholics and Protestants.
For the sins of Catholics throughout the ages for violating “the rights of ethnic groups and peoples, and [for showing] contempt for their cultures and religious traditions”. (March 12, 2000, during a public Mass of Pardons).
For the sins of the Crusader attack on Constantinople in 1204. (4 May 2001, to the Patriarch of Constantinople).
For missionary abuses in the past against indigenous peoples of the South Pacific (November 22, 2001, via the Internet).
For the massacre of Aztecs and other Mesoamericans by the Spanish in the name of the Church.