A modest proposal for "incubating" new articles
Whether you move it to a sandbox or an incubator or you delete it or you tag it for deletion my fear is that the newbie will still feel that their article has been rejected. If we want to reject their article and we clearly explain why then that should be OK, but if their article can be rescued then I believe we should do so in mainspace.
See related topic "#Consider the en:WP:Article_Incubator" about current rescue of some deleted articles. In general, the support needs to be organized, and a deadline (even as 10 days) might seem overwhelming to a rare user who only imagined the promise of "anyone can edit" and now is faced with a deadline, to learn everything needed to save an article, in a get-a-life effort to abandon their home life and react quickly, before the looming threat occurs. Having seen numerous articles scarred by the shocking en:WP:AfD banner, I must also conclude that such intense, dire warnings of the ominous, impending "fix or delete" are equivalent to a long, protracted, slow-motion (and even cruel) death sentence to a new article. I have seen it far too many times: several people say, "Hey, I'd like to work on an article about Xxxx", and then when "Xxxx" is finally created, but soon tagged for WP:AfD, then even with 7 days to add their, previously, enthusiastic edits, the effect is, almost always, a death knell, a bell tolling of the approaching axe, and user participation nearly always halts (except for category setters). In fact, I think some (many?) deletionists fully realize the successful use of the mechanical witchhunt of attempted speedy-delete, followed by the shocking WP:AfD banner, and then those numerous, repeated, ultra-negative condemnations of the article. At that point, call in the medics to assess triage, to decide if there is any future potential for moving the article into the en:WP:Article Incubator.
After 6 years of WP, I have never seen, ever, a civilized approach such as, "Gentlemen, let's list the positive factors of the article, and focus on potential benefits of quick improvements, and then re-assess the updated page, to see whether this article can be saved." No, never have I seen that: it would be too much like educated people, collaborating, to reserve judgment and try to focus on an objective, neutral viewpoint about a topic. Instead, the reality seems like hate-mongering: many people are just, simply, ruthlessly vicious about their insistence to censor a topic which they, personally, want to see deleted. In fact, I think a major reason why many insulted people remain, after a vicious WP:AfD, might be that, perhaps, they plan to get revenge on the people who pushed to delete their articles. It gives them a reason to return to a hostile, negative evironment, despite the instinctive revulsion against returning.