You are right. The build up of that was so good though that you felt the tragedy when he stopped lying to himself.
I think everyone were on board on the sympathy train from the start. And I wouldn't say this isn't a bad aim to go for.
Having the showrunners then say "we want you to feel sympathy for him, like for example Walter White" they now have to regress his arc. Especially since Sauron now literally told Galadriel his plans of ruling over everything and he had no sense of remorse and we have no reason to feel sympathy for him. He has to go from being all out evil to a character being forced in a difficult position and then resulting in doing bad stuff and then fall in love with it. If I remember correctly plenty of character tried to "fix" Walter White(Wife and Jesse tried to steer him off the path numerous times) and it's only when he finally admits to his wife (i think) and himself that he loves what he does the "hope" is lost. Up until that point people had that hope of him choosing the right path.
What hope is there to lose with Sauron at this point?
I think they are wanting to make something like this. Make it seem like he is forced into something and the audience should hope he goes on the better path and maybe even fall in love with Galadriel and vice versa and then we all feel he can be fixed and then we feel the loss of help when it's revealed when it can't be done.