Go to the hub, and click edit. At the top of the page, there will be an explanation about why it needs editing. Take a deep breath and look at the hub in an impartial way. Does it have the problem that they mention? If it does, fix it and republish. If it doesn't, or the explanation is too vague for you, then send an email to firstname.lastname@example.org and ask for further clarification. The Learning Center may also help provide some guidance.
By the way, the length time a hub has been published and its popularity has nothing to do with the moderation. Someone might have pointed out the issue to the moderation team by flagging the hub, and the moderators must have agreed.