But as to your premise as of who, in that situation, would enter the kingdom of heaven, then yes, you are correct, and I agree.
I am telling you such a transformation is not possible apart from divine intervention. And, divine intervention is possible to each one who would simply and sincerely ask it of the Creator. It really is an amazing thing.
What of those innocent who suffered at the hands of the brutal regime? Each person has an inborn knowledge of the Creator. Apart from children under the age of reason, if these people chose to embrace the Creator then they too would enter heaven as well. The tragic manner in which these innocent victims experienced death has no bearing on whether or not they entered heaven. Like you and me, it is what an individual personally chooses to do with the knowledge of the Creator that is the sole determining factor as to whether or not one enters eternity in heaven.
The overwhelming majority of people will be of the same the religion as their families. The vast majority of Christians come from Christian families, Jews from Jewish families, etc. Seems like being born into the right family is one the keys to staying out of the Hot Place.
It also presents a dilemma, I would think, for a Jew thinking of converting to a fundamentalist sect. He must adopt a belief that his dead loved ones are doomed to Hell for eternity.