The harrowing of hell is a misnomer. The West conflates two concepts which ancient Christians distinguished. Hades and Gehenna are different places. Hades is where the Old Testament righteous and everyone else went, and it is into Hades that Christ entered after His death. Gehenna is the final hell state that the wicked will be delivered into in the end, and as far as I can tell, no one has been consigned to Gehenna yet. Revelation 20:13-15 demonstrate the point.
>Death and Hades gave up the dead who were in them, and they were judged, each one of them, according to what they had done. Then Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire. And if anyone's name was not found written in the book of life, he was thrown into the lake of fire.
The lake of fire in this passage is of course Gehenna. The dead are still contained with Hades.
The parable of the Rich Man and Lazarus (Luke 16:19-31) is also a parable about Hades, not Gehenna. Christ makes this explicit in Luke 16:23, saying that the Rich Man is ἐν ᾅδῃ, i.e. in Hades.
The fact that people have not been thrown into the lake of fire and undergone the second death is why we should pray for their souls. Hades was changed by Christ entering into it as well—it was a cosmic event, not a one-time thing like it was taught in the West. His soul entered Hades, plundered it, liberated the righteous dead, preached to the people of Hades. Some Church Fathers speak of the ‘Sun of Righteousness’ (Malachi 4:2) entering Hades and illuminating it and transforming it from dark and joyless into Paradise for those who accepted Christ. It is this which the thief on the cross is promised by Christ. The righteous dead today are alive ‘in Christ’ until the resurrection.
Even prior to Christ, of course, we know that it is good to pray for the dead, as seen in 2 Maccabees 12:44-46
>for if he were not expecting the fallen to rise again, it would have been superfluous and foolish to pray for the dead. But if he did this with a view to the splendid reward that awaits those who had gone to rest in godliness, it was a holy and pious thought. Thus he made atonement for the dead that they might be absolved from their sin.
The dead encounter aerial toll-houses immediately after death as well.
I think those genuinely ignorant of the Gospel today benefit from the Harrowing even today.