Eternal life in Hell is eternal death - it is to be self-poisoned, whereas eternal life is health beyond our best imaginings.
It’s not that people don’t make the cut, so much as that they refuse the Friendship of God. By our nature, which in its state without Him is sick & dying, & without Christ, this is something we all tend to do - we are alienated from Him. And this alienation is a pathological state for us to be in. We can go to Him, only according as He first comes to us. ##
Why doesn’t God simply annihilate these people? In hell, they’re obviously doing no good to (a) themselves, (b) the people in purgatory, (c) the people in heaven, and (d) God himself. What, then, precisely, is gained by torturing people?
ISTM that the question relies on eternity’s being a sort of time. It’s not. Unlike time, it is without duration - there is no succession of moments in eternity, to allow us to say “that was then, this is now, that will be in the future”. Eternity involves total instantaneousness - a bit as though all time had been crushed into an infinitesimally small dot, only more so. The Big Bang can act as a metaphor for, or a picture of, eternity. God is His Eternity - it is God Who is the “heavenliness” of Heaven.
At any rate, it’s non-temporal, & non-successive.

So the life of the Blessed “now” is all the life they have, & all they “will” have. As it is non-temporal, so is hell - damnation is not happening “now” - it is not in fact possible to talk about it, because there is in a sense nothing to talk about. And it is a state of being which is totally meaningless - God alone gives creatures meaning, and these creatures have refused Him. So they lack everything they are meant to have - meaning, purpose, integrity, joy, love, fellowship, communion, fulfilment in Christ, everything. As we are not in that state, we lack the means to describe it - it is beyond words, because words are too sane for anything so utterly mad as hell - we give it too much reality by trying to put it into words. Heaven is too real for us to describe it - it is beyond language. We are between the two, using earthly language to describe unearthly things
Damnation is not life - it’s death, or “would be” if death were a possibility. It’s not. The state of the damned is like a snapshot; or rather, a snapshot is a bit like the state of the damned. Snapshots catch one instant out of a life - they freeze one instant in a life, and there is no way, in the snapshot, of going to the past of the person whose photograph is taken, nor into the future of that person. I think damnation is like that - it is the sterile lifelessness of one single instant, which has no past to look back too, and no future. So there is no hope, and so, no hope of pardon - merely the sterile fixity of the state of sin, seen in its true colours, as the hideous thing it is. And this something that was freely chosen - people preferred the state of sin to the
friendship of Christ - so they have it. For eternity. It’s the life they wanted, or insisted on - so that is what they have.
So the comparisons one sometimes comes across, of a world-wide mountain of sand visited by a bird which every billion years removes a single grain, and of how, even after the bird had removed all the grains one would have as long an eternity to eexpect as when the bird started, are misleading, because they bring time into the issue. In fact, all comparisons fall short of the thing discussed, because hell is far worse than we can imagine - because nothing could be worse, than to lose God eternally. Conversely, to gain God for eternity is so great a blessing that nothing could begin to be compared with it - it is that blessedness which is the measure of the unblessedness of hell.
Hell is several times spoken of as Gehenna in the NT; & Gehenna is the Valley of Hinnom, the old site in Jerusalem which was first used for human sacrifices, & then became the rubbish-heap for the city, where the trash was burned. Jesus compares the “place” of those who will be rejected to this valley & its smoking rubbish-heap. Which suggests that the damned are not men, but the trashy remnants of men, things that used to be human but which, having lost God, have ceased to be human, & are just “remains”, the disintegrated left-overs of being which were once human, but have fallen to pieces, & are in that state for eternity. They are no more human beings than the ashes of a burned newspaper are a newspaper - they are wreckage.
If this suggestion (which is taken from C. S. Lewis’ “The Problem of Pain”) is on the right lines, it would explain why the damned can’t repent: they are in too ruinous a state to do so; & they have no time (in a very grim sense) to do so. Damnation is the end.
If we want people, they can be found in Heaven - that is where to look for really human beings. Not in the trash-heap of Gehenna. ##