Here is the problem, the punishment is infinitely disproportionate, does nothing to reform the person being punished and show them a better alternative, and would in fact be infinitely evil.
What makes you think that someone who'd be worth a continued chance at redemption would be in Hell?
Forgiving someone 700x7 times is love, forgiving them forever is insanity and we'd all be stuck living in this world.
On to a related question, the problem of suffering/evil. Why does this exist? Why does God allow it? Why does God cause suffering? Why does he behave in ways that seem at odds with his teachings?
You don't earn friends by locking them in a container and forcing them to hang out with you. If God did not want beings born with the option of evil, He'd constantly brainwash them or would not bother with the creation of life at all.
Eternal suffering in Hell negates this, which is another reason I have to throw that doctrine out. What is so important about free will in relation to the problem of suffering/evil?
Free will does not remove consequences for exerting that will. If you play with explosives, expect to lose a limb. Nobody in Hell saw the path to Heaven and chose to go down it. And it's only my head canon, but who says Hell would not just be everyone exerting their own unsavory form of free will to everyone else?