The best explaination I have read explaining how the dogmas that there is no salvation outside the Church and that those in invincible ignorance of the Gospel who follow the natural law carefully can be saved is that of Bishop George Hay. I believe the Church teaches that it is not possible for fallen man to remain free from mortal sin for long without the sacraments, so that means non-Catholics are in mortal sin. In order to be saved they must convert. If they seek to do God’s will by following the natural law and striving to know the truth then they will be guided into the Church by God’s graces and providence. We cannot be sure that someone who appears to have died outside the Church has done because we do not know what passed between that person’s soul and God in the moments before death, but if they did die as they lived then they are in hell. Those who do die as Protestants etc. do go to hell and that is why we must convert them.
If anyone decides to look up Bishop Hay’s work, be careful, because one of the websites containing it is run by sedevacantists.