This is something of an issue, not just on this question and not just on Health Stack Exchange. A lack of enough high-reputation users to close and reopen questions in any sane amount of time on a regular basis is a problem that most small beta sites face, and it's not an easy problem to solve.
As I see it, there are two options. The first is to get more community members, so there are more people around to close these blatantly off-topic questions. Currently, about 50 people on Health have close/reopen privileges, including the three moderators. Not all 50 are regularly active - before today, I hadn't done anything since October, and not much else since July - and from what I can tell, only a fraction see all or even most of the questions that get asked each day.
Improving this, though, is far from easy. Community Promotion Ads can help traffic and add new members - I don't know the exact statistics - but there's no guarantee these users will stick around long enough to gain enough moderation privileges. Conversely, you could turn internally and try to get current members more interested in the site itself and in moderation - getting them to ask new questions can help show others the scope, but it can be difficult. That said, you can't force people to care, or want to use the site.
The second option is for moderators to be a bit more aggressive when it comes to closing. I moderate three sites, two of which have roughly the same community size as Health, and a bit less activity - although we get far fewer off-topic questions there. I still see problems in getting five community users to close some questions, though.
What I've tried to do in some of those cases is get involved sooner - that is, mod-hammer clearly off-topic questions when there are only two or three other close votes. There's no sense in waiting for days and days and days. I can see waiting a day or two - in this case, I don't think michaelpri did anything particularly wrong - but quicker moderator action can stop some of these questions earlier. I, for one, am absolutely fine with moderators on this site acting unilaterally in such cases if it's needed to stop these questions. Others may agree or disagree; at any rate, I think that's the best possible solution in the short-term.
I don't want to tell anybody here - moderators, normal users, or anyone else - what to do, especially as it's been a while since I was here. But from my time in Stack Exchange facing this issue, I can tell you that there are really just two classes of solutions. The community here can choose which of the two paths it wants (or some synthesis, or neither), and I fully support a new meta discussion explicitly addressing that.
In the meantime, though, keep in mind that Health Stack Exchange is still helping people. I vote to make like Winston Churchill and Keep Buggering On.
After a week of comments by Carey Gregory, Frank Dernoncourt, and Fomite, I think my mind has been changed a bit, and there's something else that needs saying. It's on the subject of answer moderation, and so strictly not as relevant here, but it's been brought up in comments, and I feel I should address it.
If people are leaving a site, that's a problem. That statement is undeniable and irrefutable. If people who really know their stuff are leaving, that's an even bigger problem. So perhaps more active moderation is batting down some of the poor answers that pop up from time to time, but it's also discouraging some of the really good ones.
Moderation like this is a battle of signal versus noise, where the signal is the high-quality contributions and the noise is the crap. The community has to decide how many poor answers it's willing to let slide in from time to time if that's going to keep good contributors here. I think - and here's the perspective as a moderator of other sites, who's gone through part of this same discussion - that we the community and we the moderators often choose to purge most of the noise early on in a site's life, and that can be achieved by being really tough on answers that don't meet a certain criteria - in this case, ones without sources. You get a high signal-to-noise ratio by lowering the signal (unintentionally) and the noise (intentionally) by equal amounts.
I don't think that's always a good idea.
Once you choose a path like that, you have to stick to it. I wasn't here early in the life of Health Stack Exchange, so I don't know what happened; I'm speculating. But it looks like folks decided to go with the hard-handed approach. And it makes sense, to a good degree. There's too much absolutely terrible advice out there on the Internet, which I think some of the medical professionals here may recognize. So you quell the bad stuff and try to raise the good stuff.
Here's the argument against that - and not just because it seems like it could help retain community members: let the voting sort the wheat from the chaff. The more people who know the right stuff, the more people who can downvote the terrible ideas - and then write the correct answers. In other words, it's okay to let some could-be-better answers in if we trust each other as a community to correct them. Let the voting have the best answers rise to the top, and let the poor stuff be buried in a pile of downvotes.
I'm normally one in favor of heavy-handed moderation because I've seen a lot of absolutely terrible posts on beta sites. A lot. But I think I've been convinced that that's not really working on Health Stack Exchange. Scratch that, it isn't working. I don't know all the ways in which things can be lightened - I trust the users who feel the moderation's too heavy to specify all of that. But if it's going to bring back a more knowledgeable userbase, then here, I'm all for it.