Why are there suddenly lots of Close votes for Review. Many of these are 12 months old and have no answers (which is itself an indicator it is not a sensible question). It is hardly worth the effort to determine the reason - any question this old with no answers could be automatically deleted.
I think I can shed some light on the "suddenly" part of the question ;) The other parts are already addressed I would think, especially why the queue is not emptied these days.
The last days I went through some of the unanswered questions (not all of them, maybe 200 or so) and flagged some as close-vote. Note that I did not flag question to be deleted for just being old or unanswered but only specifically those that I deem off-topic (and a few cases where the OP failed to provide requested information). While all of those flags could (and should) be discussed on a per-case basis it's certainly not a nuke-all-old-questions approach.
Lack of an answer does not mean a question should be deleted, It could mean that the problem is unsolvable, and hence has value for others. Several recent questions have asked about updates to some of these older questions. Many times answers are possible to questions that were not answerable in the past. for example how to install a package that was only available for Raspbian (Jessie).
There may be cases where they can be put on hold or closed, but the existing process (flagging) should be sufficient to address the issue. I think the strategic approach is preferable to the atomic option of deleting all old unanswered questions.
Because when we graduated, as observed here, the daffy SE system significantly raised (as in, much more than doubled at least some of) the privilege levels, because we are all big boys and girls now and things should be harder for us.
Notice the threshold for casting close and reopen votes is now 3000 points. I believe before it was actually 500. This means we now have 14 users capable of using the queue, whereas before we had more than 150.
"Why, that sounds dysfunctional", you might say. I would agree, but as I was trying to hint at in my answer to Jacobm001's question, the SE community at large (read, those who frequent Meta and the actual staff) can be extremely ideological in the bad sense, meaning the idea is more important than the reality, and even when the idea clearly does not work, there is always a reason that can be concocted to justify sticking with it, because the idea was perfect in the first place and it would be impossible for reality to contradict that.
Of our 14 users who can now use the queue, 3 are the mods, and the majority (including me, for a reason I'll get to in a moment) haven't looked at the queue since we graduated and likely many of them never will.
It of course only takes one vote to put a question in the queue, and dollars to donuts a big percentage of people who've done that (vote to close) don't deign to bother with the close queue itself.
Since it takes 5 non-mod, non gold-star-in-tag (I'm not sure if we have anyone in the latter category) votes to close a question, the chance of the queue working in that sense at this point is very low -- I suspect not one single question has been closed by this mechanism since we graduated and it will be a long time before one is.
Part of the issue is perhaps that I don't look in the close queue. I've said this a few times elsewhere, but my attitude is that the community should have the opportunity to do this without me having to act by fiat all the time (so I'm strongly disagreeing with Steve on this point, that flags are an appropriate solution). Note that I've already closed more than 1000 questions, more than 10% of the total, and 4x more than Steve who I guess is the runner-up. Many/most of these were actually questions from years ago; I spent a lot of time going through old cruft in an attempt to improve our "unanswered questions ratio" looking for things that either had an answer that deserved an upvote or should have been closed.
The system is not intended, I think, so that sites are effectively maintained by one or two all powerful figures -- that is not what the role of moderator is supposed to be, and that is not how it works on most other non-beta sites. Unfortunately, it is also a one size fits all system and completely hamstrings itself in this case.
So, I'll start using the close queue (this is more in line with the ideology, of course, because, "You should vote to close because you think the question should be closed and not leave it up to the community to do so"). I also intend to see what I can do to get our privilege levels adjusted or (gasp!) change the system, since there are other members and moderators around who also see it as highly problematic. I'm very busy in real life right now though, so I will not have time for at least a week and possibly not until the New Year.