It doesn’t address the eternal suffering of the fallen angels
Gehenna was a garbage dump, not a furnace. It had both worms and fire to consume. And in both cases it points out that the force that consumes does not die. Again, an analogy (for obviously Gehenna is not the literal subject of Jesus’ words) for the fate being final. They are gone. Permanently.
Maybe you could clarify, then: what, exactly, is your objection to eternal hell for the damned? I’d been under the impression that you found it to be too cruel of an idea to attribute to God. Was I wrong?