I don’t agree with it, either.
I like Bilbo, but as I’ve said before, he’s the audience surrogate – that is, if the audience is a clueless white man. Bagginshield (unfortunately) isn’t canon, so we can’t say he spends the rest of his life grieving for Thorin as Thorin was meant to be grieved. It’s arguable that his time with the Ring affected him very deeply and negatively, but I don’t like that he never faced any clear consequences for what he did to Thorin. Thorin DIED. Bilbo…well, as you said, he went home rich, and in the books, there was never a single apology.