In my opinion, "what is a good and immediately effective strategy to learn maths?" is a canonical example of a question that is "too broad", and perhaps also "primarily opinion-based".
Some of the other threads you link to are not beyond critique in that regard, but most of them seem to at least indicate a background, and reasonably scope the field of maths under discussion.
On the other hand, you expressly preclude any specification of such sorts. This, in my opinion, makes it perfectly valid to close as "too broad".
The solution, therefore, is simple: narrow down your question to be reasonably scoped.
NB. However nicely you couch it in words, being the owner of a meta thread does not justify you declaring "extraneous and irrelative" any possible critique to your point of view. Taking such a stance may be perceived as condescending, stubborn, and/or arrogant.
Similarly, some may find your choice of words to transcend beyond eloquence and enter the realm of grandiloquence. Furthermore, I think it's good to take into account that this is an international website, where many users' command of English will necessitate a dictionary to decipher your post.
Eloquence is a virtue; an aid. Not a goal in itself.
Response to supplement:
Some reasonable scopes are e.g. your links 1, 3 and 5.
On the other hand, 6 (the one you allude to as invaluable) is not invaluable on the grounds of its reasonable scope. It just so turned out that this not-so-great question received the attention of some people who wrote useful things on learning maths.
But that feat alone does not make the original question good. What is (to me, at least) even more obscure is how your question (in its current form) would provide added value to the previous threads, were it to be reopened.
The phrase "expressly preclude ..." referred to a comment that you had posted in response to Prahlad Vaidyanathan's (along the lines of "I don't want to learn anything specific, I'm just asking about general advice." IIRC), but which was since deleted (and replaced with a different one). Now it is not hard to conclude that this part of my answer does no longer apply.
As to your second paragraph, I get now that it refers to the meta thread. In my original reading, it referred to the main question. And my original response seems a reasonable fit to "an intimation of disallowance or declination" because I think it should remain closed. It is this reading that I based my comment on. It was strengthened by the strong emotional claims about not comprehending the closure and considering the question exemplary.
In conclusion: Indeed, your question is not worse in "broadness" than some of the other threads cited. But, this does not mean that it's not "too broad". As I see it, the other questions got lucky, and would've been good candidates for "too broad" closure. However, the good answers that were given alter my judgement enough that I consider it defensible to keep them open.