Q:

Okay, the sandbox didn't work. We still have a quality problem; let's figure out how to address it

As of today, the riddle sandbox is no longer mandatory. The close reason related to it has been deactivated, and the requirement has been removed from the sandbox text. It was an experiment to see if it would be sustainable and effective going forward; for a variety of reasons many of you have pointed out, it didn't work. (We also screwed up at judging the amount of support an idea needs before it has consensus, and offering enough time for a thorough discussion of the merits of ideas.)
But that's fine; everything is reversible, and it gives us all a better sense of the capabilities of the system going forward.
The sandbox itself is probably still worth keeping around, though without the mandatory requirement, because as a tool it could still prove to be valuable to anyone who decides to use it. Even if it's never touched again, it does no harm just sitting there. Unless someone thinks of a good reason it shouldn't be there at all, this is probably what's going to happen.

However, this still leaves us with a quality problem. The idea of a sandbox requirement came about in response to a growing sense that riddle quality is dropping on the site, and that it's becoming more heavily populated with low quality content. (Number sequence and cipher puzzles were even tacked onto the proposal's discussion for similar problems.)
Most of what I said regarding quality in the riddle sandbox proposal I still stand by:

Riddle quality is dropping. I think most of us have seen it lately: there’s been a slow slide in effort and energy put into riddles, and it’s starting to seriously hurt the site. On Stack Exchange, our goal is to optimize for pearls, not sand, and right now, we’re very much not doing this. If we were, it would not only push the quality of the site up, but also drive us to advance the state of the art.
Nowhere else that I know of on the internet do people collaboratively come together to develop new puzzles - including riddles - and that’s not something we want to stop. However, we need to do something to sort out what makes a riddle high quality for this site, and set better quality standards.
So it’s time for us to set aside some energy and effort to sort this out, and start over with a better structure in place to support riddles.

This is the discussion that I want to see continue. I think most of us recognize that there is a problem, and Hugh Meyers even offered insight into why the proposal might have gotten the sort of initial support that it did, even the idea wasn't ultimately very good:

The massive support the proposal had in its first day shows the widespread recognition of the situation and a strong desire for some sort of a solution.

I don't want to belabor the point, rehashing stuff you've probably already read and read again. Instead, it's time for you all to drive the quality discussion on meta.
What we've been doing, bringing these proposals to meta, is partially intended to try and drive discussion. This is where these problems are solved, and there's definitely a solution out there; we just need to find it. (And yes, perhaps more carefully consider its implementation and subsequent effects before diving in head-first.)
So please, please propose and discuss ideas on meta. Don't let this issue stagnate; mods are three of hundreds of community members, and we're all going to get the site that we fight for together.

A:

Totally agree with both of Rand's answers, however, I think we need to hone in a little on what the new close reason should be, so I thought I'd add my thoughts...
New close reason
See Rand's answer for reasoning/precedent, however, I believe the text should be a little different. The primary aim should be to catch/close low quality content, which can be redirected to a sandbox where it can potentially be improved, so I propose the following close reason:

Low Quality1 - In it's current form, this puzzle does not meet Puzzling's [community quality standards]2 and needs refinement. Please take the time to read the guidelines and improve your puzzle. If you would like assistance, you can post your puzzle to the [Puzzling Sandbox]3 to get guidance from the community.

1 - Could possibly be renamed to Needs Refinement or something equivalent, to make it slightly less inflammatory/accusatory - we don't want to scare off innocent newbies.
2 - Would link to the meta post described in point 3, below.
3 - Would link to the either a new general purpose sandbox for all puzzle types, or could possibly be reworded to say "...post your puzzle to the [Riddle Sandbox], [Cipher Sandbox] or [General Puzzle Sandbox]...", if we wanted things split up into chunks.
Community Quality Guides
To keep the close criteria as objective and consistent as possible, we could create an faq tagged meta post, with individual answers per "major" tag (i.e. the big ones, that are currently problematic/controversial like riddle, mathematics, cipher, etc), plus a "general puzzle" catch-all, to help define exactly what constitutes the quality standard minimum, in as clear and unambiguous terms as possible.
We would obviously need individual discussion posts to gather consensus on criteria for each puzzle type above, but there's already some great content here on meta that we could draw from (eg. for ciphers, mathematics, etc). To give you an idea though, I imagine each "answer" would look something like the example below.

Indicative example of a Community Quality Guide, take with a grain of salt... the important stuff of this post is above.

Riddle Quality Criteria
To meet minimum quality standards for Puzzling, a riddle must:

Have a single "obviously correct" answer
Be more than just a straight description of the solution's features
Describe a common everyday object/concept (or be tagged with an appropriate secondary tag, such as trivia, movies, literature, etc to identify that specific domain knowledge is required)

Additionally, your riddle must meet at least three of the following criteria:

Use well structured meter and rhyme
Be concise and well written
Use a creative/unique structure or presentation
Employ letter/wordplay
Make use of metaphor/polysemy/turns of phrase

A:

This may not make a huge difference, but since new users are often high on the blame list for the poor-quality stuff, we should
change the Puzzling Tour to actually reflect this site.
I think this is probably a low-effort but some-reward step we could take, so why not do it.  If you don't think it needs to be changed, go take the Puzzling Tour right now and try not to furrow your brow.
At least some of the recent poor quality questions (example, example, example) come from users who do have the Informed badge.  That means at least there's one potential point of intervention to communicate something to new users.  Right now, nothing Puzzling-specific is on that Tour, and in fact you could argue some of the stuff is Puzzling-detrimental.
And I think Emrakul indicated (as a comment on this post) that we do have some control over this.  So...why not?

A:

A chatroom for detecting and discussing low-quality puzzles.
Whether or not we implement a new custom close reason for 'bad' puzzles as proposed in my other answer here, we need people to be aware of it and of any new puzzles coming in that should be closed using it, otherwise there's no point. Emrakul mentioned in comments on another meta post that part of the reason why moderators have been closing too many questions unilaterally is because the community haven't been active enough in closing questions which should be closed.
I propose creating a dedicated chatroom for crap-catching. It would have a feed to post new questions into the room, and in it people would discuss the possible closure of particular questions. This would:

be easier to keep a constant eye on than the Close Votes review queue, since people could hang out and chat idly in between discussing questions to be closed
encourage active community discussion rather than just hitting the "Close" or "Leave Open" button, which would be helpful in shaping policies for the future
draw people's attention to questions in need of closing quicker than the review queue does, since no initial VTC would be needed - all new questions would appear on the room feed.

For the first while, when not many people frequent the chatroom, we might find that more or less the same bunch of users are closing many of the questions, but as we attract more and more participants to the room and the project, that should change. Note that users with <3k rep would also be welcome to join in: even though they can't actually vote to close questions, they can still flag them for closure and take part in the discussions around them.
Of course we'd have to publicise this room as much as possible to make people aware of its existence. Ways to do this might include a featured meta post linking to it and superpings from any chat mods involved to bring active community members into the room.

