Firefoot, we seem to be saying the same thing. What happens to Frodo is wrong - everyone in the story seems to
know that - Sam certainly does - his last words to Frodo show him struggling to accept the
wrongness of his fate. The world is wrong, & what happens to Frodo is wrong. It is the 'way things are in the world' & has to be lived with, but it must still be acknowledged as 'wrong'.
To stray into a 'dangerous' area - Christ comes to die, to save the world. If he hadn't died on the Cross, if he'd lived a quiet life as a carpenter, got married, had kids, grown old & died peacefully in his sleep, that would have been a 'good' life for him. But no salvation, no hope beyond the world, everything would just have carried on in the same old messed up way. So, he had to die, as he did. But still, when we look at, think about him hanging there, being tortured to death, our instinctual response is that's its
wrong, that it should not be happening. Intelectually & theologically we might understand why it happened & even be thankful for it, but on a gut level we what see is the 'wrongness' of the world symbolised in that one event.
Now, back to the 'plot
Moral choices are not made in a vacuum, & Frodo is put in a postion of having to take up the responsibility laid on him, or end up feeling a worse failure than he does in the end anyway. He is manouvered, by Eru, among others (Gandalf tells him he was
meant to have the Ring - & not by its maker). And ultimate responsibility lies with Eru, not with Morgoth or Sauron, because Eru states that none may alter the Music in his despite.
So, does Eru have any 'moral' responsibility for his 'intentions', for what happens to individuals as a result of the changes He does or does not allow? Surely He must, if he can demand that of the inhabitants of Arda? Can Eru be held to account? Would He also require, perhaps, forgiveness from his creatures?
And please remember, none of this is to question God in this world - (though Jung seems to ask these questions about God in his 'Answer to Job'). Eru is a character in a story, God of Arda, not of this universe & we can analyse his behavour with just as much right as we analyse that of Frodo or Sauron.