If a recently asked question which is exactly the same as (or is contained in) an old question then why does marking the new question as a duplicate require the old question to have an either upvoted or accepted answer? I agree that a violation of the above conditions means that the question doesn't have a satisfactory resolution documented but it doesn't mean that we should pile-up similar questions. Rather, we can mark the new question as a duplicate and direct the reader to the old question through something like "this question already has been asked here" and thus, if someone wants to answer the thing then they can answer the old question.
Also, if we allow the new unoriginal question to exist owing to the fact that the old question is not well answered then it might happen that in the future, both questions get answered (or worse, the new question gets well answered and not the old) and then I am not sure which question should we mark as the duplicate. Or should we just let two same questions exist with a bunch of good answers at one place and the other bunch at the other place?