Eman/mike: who are the “not good” boys marrying?
Often, no one, which is why it is relevant to the “shidduch crises”.
Your analysis is irrelevant to the question of why we have so many older single girls and so few older single boys.
That’s true. But if some of those “few” older single boys (and there are still plenty of them, just not in proportion to the girls) would get married, an equal number of girls would get married as well.
As far as a solution, that’s the point of the NASI project.