you reason well in principle, but unfortunately, there had also been, and there will also in future be, an unfavorable change in the soul's position/state during the course of the eternity of eternities, every person who commits spiritual unrighteousness/wickedness/lawlessness or causes harm/suffering to their neighbor risks falling to a lower position, which can make them have a worse fate and suffer more in the next eternity than they had had and (had) suffered before it, and this is what is called "death" in the Bible, namely the deterioration as a whole, i.e. to "die" (biblically) means to deteriorate (one way or another, or in many respects), that is why Solomon says:
Ecclesiastes 9:1-18 (NIV) "I reflected on all this and concluded that the righteous and the wise and what they do are in God’s hands, but no one knows whether love or hate awaits them. All share a common destiny—the righteous and the wicked, the good and the bad, the clean and the unclean, those who offer sacrifices and those who do not. As it is with the good, so with the sinful; as it is with those who take oaths, so with those who are afraid to take them. This is the evil in everything that happens under the sun: The same destiny overtakes all. The hearts of people, moreover, are full of evil and there is madness in their hearts while they live, and afterward they join the dead. Anyone who is among the living has hope —even a live dog is better off than a dead lion! For the living know that they will die, but the dead know nothing; they have no further reward, and even their name is forgotten. Their love, their hate and their jealousy have long since vanished; never again will they have a part in anything that happens under the sun... I have seen something else under the sun: The race is not to the swift or the battle to the strong, nor does food come to the wise or wealth to the brilliant or favor to the learned; but time and chance happen to them all. Moreover, no one knows when their hour will come: As fish are caught in a cruel net, or birds are taken in a snare, so people are trapped by evil times that fall unexpectedly upon them. I also saw under the sun this example of wisdom that greatly impressed me: There was once a small city with only a few people in it. And a powerful king came against it, surrounded it and built huge siege works against it. Now there lived in that city a man poor but wise, and he saved the city by his wisdom. But nobody remembered that poor man. So I said, “Wisdom is better than strength.” But the poor man’s wisdom is despised, and his words are no longer heeded. The quiet words of the wise are more to be heeded than the shouts of a ruler of fools. Wisdom is better than weapons of war, but one sinner destroys much good."
so the "dead" are the ones that have fallen to lower positions and deteriorated and thus become (as it were) "forgotten", i.e. their qualities have come defiled because of their sins, for the vanity isn't/can't be interesting to the true One, because He is "Light" and there is/can be no "darkness" in Him at all
Blessings
