Heb 10:26-27 - if sin after receiving truth, judgment remains
Most Christians believe in no salvation outside the church. The issue is what does “Church” mean. The Catholic position has slid all over the place in the last few hundred years. In the past, the Eastern Orthodox were viewed as schismatics and outside the Church. As were all of what are popular called Protestant churches (though some of the Lutheran synods were in a odd state till after Trent, but that is another issue).
Now the old tradition did say that if you were born, say, a Russian Orthodox, you MIGHT be saved if you never committed a mortal sin IF you had no real knowledge of what the Catholic Church claimed. BUT that was viewed as a very slight chance. The current view is much looser than that.
We shall see how this doctrine changes. I suspect it will be cut down to a much more narrow thing as the old liberals die off.
“if sin after receiving truth, judgment remains” What version is this? Your Douay-Rheims Bible says: For if we sin wilfully after having the knowledge of the truth, there is now left no sacrifice for sins. The NIV says: If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left.
The key word is “willfully” or “deliberately” keep on sinning! Now is that something a Christian would do?