If you really think a question is of such little use to anybody other than the poster that it is detrimental to the website, then I would suggest voting against it. We want to maintain the interest of our community by optimizing for pearls over sand and the voting system is balanced to accomodate for liberal votes against questions for this reason. The voting score reflects the community's aggregate interest in the question, and helps people just finding it to evaluate of how much interest the question is before they even click into it for more details. However closing questions is different, because if done without due discretion it can prevent a gem of an answer being contributed. In other words, it can optimize against both sand and pearls.
Beyond that there is not really much of an appropriate measure: Commentary is mostly reserved for constructive criticism which should lead to the improvement of the post. If the subject matter is inherently uninteresting, then no amount of feedback is going to improve the question, and if you have a suggestion to make the question more interesting then it would probably be better received if you focus on that instead of discouraging the reader by prefacing it with the narrative that the question isn't worth the trouble.
Flagging and close voting is mostly reserved for content that is problematic to the extent that it should be outright deleted from the website if it remains in its current state but too localized questions likely do not merit such extreme measures. It is not like we are a paper resource which is bereft of space to address every possible question, and it is part of our mission statement here at Stack Exchange. If a question is otherwise well-asked, and possible to answer in a constructive manner, it is effectively harmless and its removal only denies the people who are interested in the question the opportunity to address it.
Something which absolutely needs to be kept in mind is that Too Localized was a network-wide closure reason which was not merely imperfect, found to be highly problematic. It was one of the closure reasons that was eliminated as a result of the war of the closes, because it covered too many vague circumstances. You could argue that if we bar questions that are "only relevant to a small geographical mass or specific point in time" that most of our questions dialectical or historic usage should be discarded, which is something I very much doubt that most of our current intended user-base wants.
The best reason we had for too localized is perhaps because some questions were of too little interest. However the problem with that is that it is too much of a judgement call to reasonably make with any degree of consistency, which is why a more restricted too narrow closure reason was rejected as a replacement. If somebody was interested enough to ask in the first place, then it isn't too much of a stretch to assume that other people may take interest in the same problem.
If other people do not take interest in the same problem, then the question will probably remain unanswered anyway, meaning that there is not even so much as a need to close the question. Moreover, these unanswered questions may serve to our benefit later if we are proven wrong and somebody comes and decides to answer it with a compelling answer, but if we close those questions prematurely, then we are denying the possibility of that even happening. This is all the worse if the answer reveals matters deeper interest.That is why we have an unanswered questions queue and possibly even the necromancer badge.
Think about it this way. Should we really have a closure reason that is simply a coded method of saying "this question bores me for no certain reason?" Honestly, I think not.
Now if we had a finite amount of space at our disposal, that could be harm us by interfering with our ability to address more noteworthy subject matter. However we are not so constrained. We are not like formal dictionaries and other early reference works, since we are not limited by how many pieces of paper can be bound together in a few volumes. A few such questions here and there doesn't really seem harmful, so long as we're not getting them so often that it noticeably detracts from the overall usability of the website, and if we are, we can probably categorize the questions more meaningfully.
Now if answering a question is effectively meaningless and risks doing more harm than good in its present state, I can understand closing it for that reason, but the too localized closure reason never really did anything to identify such a fundamental problem.
To put it another way, if I decide spend a few hours pouring through references and explaining that there is no such thing as a paraphrase bracket in the English Language of my own volition, is that really such a bad thing that you really have to take active preventative measures against it? That question went unanswered for months, and I genuinely doubt that it is a matter of broad interest that will make a meaningful impact on many people's lives since most people probably don't even think about paraphrase brackets. However, I had myself wondered about how to appropriately paraphrase before, and the few people who do take interest in the matter seem to appreciate my answer.
Besides that, if we expect to operate in a community of people who help each-other learn, then answering the boring questions some other people might have, where possible may actually inspire the people who receive constructive answers to pay the favor forward, and serve to exemplify how that can be done. It's also a very good way to potentially pay back the other members who have decided to help us with questions of ours that they may have also found to be inane.
Another concern is that there is already very little middle ground between the Primarily Opinion Based and General Reference criteria, and I don't think we really need to narrow that ground even further by taking a very severe approach against questions which can only be vaguely described as "too localized". Voting against a queston's score seems like enough of a corrective measure here.
Finally, we use the questions and answers format to suss out which questions are of interest, and need addressing, but there is a certain price to be paid for that. The unique appeal of a questions and answers website to questioners, who we certainly do need, is that they might be able to gain some personalized assistance. It seems obstructive to that purpose to just uniformly block questions with no discernable problem other than what may just be personal disinterest.