When should I use "a" vs "an"? is a very elementary question that hasn't been closed. I've seen lots of other questions, not so elementary and obvious as this one, be closed five or ten minutes after they had been asked, on grounds they were off-topic. Can anyone tell me why? It's preposterous that someone should have got so many votes by answering such a ridiculous question. In fact, many more votes than I have seen for any other question on EL&U.
The question you have linked is from 2010. Back then, ELU was significantly more open to receiving any questions about English. The push to reduce the number of "too basic" questions only officially started in 2011 with the creation of the General Reference close reason.
Also, as far as I know, there is still no official policy on ELU to close questions that are simply "too basic". Most of the "too basic" questions that get closed are closed as General Reference which, as I noted, didn't exist back when the question was asked.
At this point, the question has become a common duplication target and trying to close it now would not significantly improve the site. The primary reason that people find "too basic" questions problematic is that it takes time to answer them and if the site gets clogged with too many "too basic" questions then the regular contributors will suffer from burn out and vacate the site. This concern obviously doesn't apply to a question asked over four years ago and especially not one that already has 11 answers.
Therefore, I see no particularly clear reason to close this question. If you are concerned about other questions that been closed as "too basic" it is possible that they shouldn't have been closed. We can certainly help address any particular examples you bring forward.