I like it. It's an examination of dream logic but it's not a dream like Blue Velvet or Mulholland Drive are.

I don't think the ending absolves William Hurt of his failure but you're right that it ends David's suffering due to that failure. I don't think it eschews a lesson because it's not Hurt who "saves" David. An unknowable higher power steps in where humanity failed utterly and completely. I think the lessons remains…

I think there's a case to be made that Spielberg doesn't overtly answer the question either considering how dramatically so many people misunderstand the ending.

It's not tacked on, it's the answer to the question.