Either it's just me, or I've there's not an "other" option for flagging. There is the box to notify moderators, but that's only for content that requires their direct attention. We should get an "other" option if the user flagging the question can't find an available reason listed to flag the question.
So... who exactly do you think sees flags other than moderators?
While it's true that ordinary users can review Very Low Quality and Not-An-Answer flags, for the most part, (including those), they go straight to moderators. That's the whole point. There's already an 'other' option - it merely specifies that it's for 'Moderator Attention' because, y'know, who else would it go to but us?
Use it wisely, use it frequently, use it sparingly, and use it well. It exists so you can make it clear that a question requires the attention of others who have more power than you to do something about it.
(Please do not use the 'other' mod flag if all the question or answer needs is an edit, for example. You can do that. Etc.)