Hell works fine with pluralism, it just doesn’t work well with pluralism and theological rigidity at the same time.
Lemme 'splain. Back in the old days (meaning the Stone Age), pretty much every valley had their own unique belief system, and their own god or gods. Eventually people could travel further for trade, agrarian societies became large, and something needed to be done about these disparate religions that were encountered through alliances, mergers, and conquests.
The Greeks formed a pantheon, a family of gods, polytheism based roughly on their alliances and mergers, but also a pantheon of the defeated (the Titans, etc) for their conquests. Similarly, the Hindus did a “multiple aspects of the same god” pantheon, which could be polytheistic or monotheistic depending on how you looked at it. Other groups incorporated the gods of other cultures into their pantheon, but mostly as demons, not gods. So that’s how you get Satan, Beelzebub, Mephistopheles, etc. Our valley worships the real god, all the other valleys worship demons, was basically how it went, and today’s “all other religions go to Hell” belief is pretty much a straight line from there.
Theoretically, Christians could simultaneously maintain their belief in Hell and choose not condemn other religions to Hell if they followed the “multiple aspects of the same god” example, and in fact that does seem to be a feature of some more modern conglomerate religions like Sikhism, Baha’i, and Unitarian Universalism. You also see this concept in statements that refer to Christians, Muslims and Jews as “people of the Book” or some such thing. Not saying many would, but there is a path out of Gehenna that does not involve rejecting Christianity at all.