on the "question in question" posted, it was initially labelled "soft-question" and "big-picture" and kaveh quickly deleted those tags.
there are many questions on this TCS site that are very broad but are highly rated. their broadness is indicated by many responses (easily over a dozen), some spanning 3 pages or so. can dig up numerous examples of that.
eg the "broad" rejection is one aspect. on this site there are tags like "soft question" and "big list" and "big picture" tags (which are nice but apparently opposed by some here) that seem like they are in mild conflict with the broadness question rejection standards. isnt a "big list" or "big picture" inherently broad? or "soft question" verging on meta? etc... ie the combination of these conflicting elements is not always totally coherent.
for example suppose the questioner asks a broad question, but nobody knows the answer and there are few replies on this site. why is that a problem? isnt that less of a problem than a question with 3 pages dozens of answers in which its difficult to determine if answers overlap or if they match? isnt that what the broadness rejection criteria is attempting to prevent?
on another stackexchange, maybe the original stack overflow, saw another approach to this-- questions that are too broad are closed after there are too many responses/answers accrued. this pattern can be seen on some sites.
(therefore would like to know or see clarified more specifically why certain questions are rejected by stackexchange standards and think that the stackexchange software has significantly expanded outside of its original scope & feel that reevaluation of some of the rejection standards in the context of new uses of the software is justified.)
also, anyone can edit questions to improve them, but this seems to be rarely done on downvoted questions here... for obvious reasons... anyway there is little interest or motivation in "rescuing" questions here that get initial negative reactions... this may be a more TCS cultural aspect compared to other stackexchange communities...
ps/fyi it is interesting to note there is a stackexchange medal that is intended to encourage/incentivize people to rescue bad questions, by getting a medal for posting a great, high upvoted answer on a negatively voted question-- last I looked nobody has been awarded that on this TCS stackexchange...