Many non-Catholic Christians don't even know what "infallible" means when it is used in Catholicism.
Infallible means that the two times a decision came up through the people of the Church, first at the parish level, then at the diocesan (bishop) level, next to the Cardinals (Vatican level) and was finally given to the current Pope at that time for the final nod, that nod by the Pope was infallible--it was not the Pope who was infallible. It simply means that when a Pope agreed with the parishioners, priests, bishops, and Cardinals that the Assumption of Mary into Heaven and Mary's Immaculate Conception did occur, that decision cannot be undone by any succeeding Popes who inherit the Chair of St. Peter.
In other words the nod given by Pope Pius IX in 1854 to the Church Community's decision that all Catholics recognize the Immaculate Conception of Mary cannot be undone by Pope Francis (or any other Pope) in 2022. That decision is known as "infallible" and has been since 1854. Pope Pius IX, on the other hand, always was and always will be as fallible as any other man.