Dom's points are all very good so I won't revisit them, but look at the broader view and hopefully address some of your points in the question and your comments.
Yes, there are questions here which seem very vague, especially if you are used to the specific questions you can get on more technical Stack Exchange sites, but a huge part of that comes down to the subject.
Music is not a science, and it does not have a specific set of rules
Music covers such a broad set of areas from John Cage's 4'33" to noisecore bands that you cannot define what makes a composition.
You can however look at standards, such as scales, modes, melodies, analysis, ways to approach composition based on your genre etc. and whenever we get questions in that are in more difficult areas we take each one on its merits, and the community here is broad enough to provide useful steer on whether a question should be closed.
And we (mods and community alike) listen to each other. I have on occasion reopened questions I thought should be closed based on a challenge from community members with specific experience in that area. So it all kind of works as a growing community.
That said, if there is specific improvement you, or any other, can describe that we can take action on (such as tuning our close reasons or scope etc) then we have done that a number of times, and expect to do again as the community matures.