The problem, through my eyes
In my opinion, the main problem is how the close system works. The thought behind it is that a non-conforming question is stalled by being closed, and the author or even other users go ahead and improve the question until it conforms to the rules. Afterwards, the question is reopened and takes part in the normal question life cycle.
As far as I'm concerned, this system does not work for new users, because they basically always give up as soon as their question is closed. They do not know about the second part of that closing process, and they lack the motivation to experience it. Instead, they turn around with a bad feeling and go look for their answers elsewhere. This happens a lot because there are lots of ways in which a question can fail the current standards.
On top of this, the second part of this clean up process hardly ever is done at all. Most users, me included, appear to expect the author to bring their questions up to standard, since - above correcting syntax - that's a very time consuming process, and bears the risk of the question still not surviving, or the edit being invalidated because it misses the intention of OP.
So even when a new users sticks around their closed question, they'll almost never experience that someone else cleans up their question, or that someone is even willing to guide them in doing it themselves.
The advice given in the close reason boxes is easily overlooked and in general vanishes behind the bad feeling having a question closed as result of your first engagement with a community like this.
- Revamp the close system, as to generally gear it more towards improvement rather than blockade. This may include a rewording in the name of the system itself, but also a stronger emphasis on how to get your question unlocked in the first place as covered in the close messages and boxes.
- Find users to help and a reliable way to connect them to new users for walking them through the path to unlocking their question. (Here, the rep threshold for chat is a strong problem for real time help, really.)
Feel free to extend, especially the solutions part.