Being a faithful Catholic, in a state of Grace is absolutely necessary to be saved.
As we have seen (post #6) that is a corruption of the doctrine of Christ’s Church which teaches through the Magisterium in Vatican II, reaffirming in the Dogmatic Constitution on the Church (Lumen Gentium) #16: “Those who, through no fault of their own, do not know the Gospel of Christ or His Church, but who nevertheless seek God with a sincere heart, and, moved by grace, try in their actions to do His will as they know it through the dictates of their conscience – those too may achieve eternal salvation.”
Bl John XXIII, Address of 11 October 1962: “…The Council…wishes to transmit Catholic doctrine, whole and entire, without alteration or deviation…To be sure, at the present time, it is necessary that Christian doctrine in its entirety, and with nothing taken away from it, is accepted with renewed enthusiasm, and serene and tranquil adherence… it is necessary that the very same doctrine be understood more widely and more profoundly as all those who sincerely adhere to the Christian, Catholic and Apostolic faith strongly desire …it is necessary that this certain and unchangeable doctrine, to which is owed the obedience of faith, be explored and expounded in the manner required by our times. For the deposit of faith itself, or the truths which are contained in our venerable doctrine, are one thing; another thing is the way in which they are expressed, with however the same meaning and signification”: AAS 54  791-792
Matthew 16:18 says the gates of hell shall not prevail against the Church. Pope Pius IX, St. Pope Pius X, Pope Pius XII, Paul VI, Bl John Paul II, etc. all have taught that those who are invincibly ignorant, have the possibility of achieving salvation. None of the Popes mentioned downplayed the importance of people joining the Catholic Church. Here one has access to the salvific sacraments. They have left room for the possibility of salvation for those who though not directly joining the Catholic Church, still could be linked to the Church, if they truly desire, and respond to whatever grace God has given them. This the Church teaches is possible through Baptism of desire and by following the natural moral law written in their hearts – those people are linked to His Church and thus to Him.