I feel like it's important that in the lore of Doom, demons aren't the prisoners of Hell, they're its wardens. They're job is to inflict suffering on the souls of the people sent to Hell because Hell and its denizens draw their power from that suffering. The Slayer doesn't wage neverending war on Hell out of some desire to punish sinners, it's actually kind of the exact opposite. He's outraged by the entire concept of there being a Hell, he's incensed by the injustice of inflicting eternal damnation on people.
That's why I hate all those "Doom is a catholic game" LARPers. The whole point is the entire theological system of binary moral judgementalism where the "impure" deserve to suffer is bullshit. The plot of Doom Eternal is that the actual biblical Armageddon has arrived and the in universe stand in for the Heavenly Host are all like "look we don't exactly enjoy the mass slaughter of the human race but that's the just the way it is, I mean, there needs to be a Hell or else how will we reinforce our own authority?" to which the Doom Slayer responds "well then fuck you too," kicks their asses and cancels the apocalypse.
