Empty, inane, devoid of value. This is a dictionary definition of the word "vacuous". Are vacuous ideas worthy of consideration? I mean no offence, but I fail to see the sensible intent behind a few questions.
Not all questions here are equally "sensible" as you put it, but one cannot rule out a priori that an issue that superficially seems "empty, inane, devoid of value" is necessarily so. A good example is Frege's preoccupation with exceptional cases involving the empty set, that is deemed "revolutionary" in a study by Gillies:
Gillies, Donald. The Fregean revolution in logic. Revolutions in mathematics, 265–305, Oxford Sci. Publ., Oxford Univ. Press, New York, 1992.
Donald Gillies: The Fregean revolution in Logic, pp. 265-305
Sometimes what seem to be the silliest questions are the best ones. For example: Do we know what natural numbers are?.
Maybe. But perhaps it is analogous to panning for gold, in which a lot of time and effort is spent manipulating valueless stuff but occasionally something worthwhile is exposed. Or perhaps it is like exercising in a gym- a lot of work is performed to no effect other than the fact that you feel better and stronger for it.
This is no new complaint of philosophical discourse. Metaphysical speculation can range from highly productive to highly absurd. WP has an entry How many angels can dance on the head of a pin which captures language I've seen in multiple places that describes how discourse can often be superficial and meaningless, particularly when detached from empirical tenets.
How would we even settle the notion of 'vacuous' and its systemic application? Perhaps 'vacuous' itself is an essentially contested concept. Or perhaps it's just a catch-all for anything one does not value. In which case no two people would like agree on everything that is vacuous and everything that is not. There is a certain hypotheses labeled law of triviality about a certain sort of psychology where people disagree on trivial matters to distinguish themselves instead of engaging in quietism.
The problem with 'vacuous' as a tag is that itself is vacuous. What constitutes vacuous? Some say theology since God doesn't exist. Is this the right use of the term? How about discussion of pseudoscience? Does is it not teach us something about demarcation? How about phenomenology if one is an Anglophone? Does bracketing have any legitimacy in the scientific world of the West? And if a naturalized epistemology is the one, true measure, does the entire Indian philosophical have any import at all? Seems quite arrogant to say no.
It seems the best to focus on the structure of philosophical content rather it's content in case it is found to be impactful in the future. Is the discourse reasonable? Is it attached to a tradition? Does it conform to community standards? Does anyone value it? If the answer to any of these is yes, it's best to let the discourse be, and simply choose to put our attention elsewhere. One never knows when an absurd idea becomes the foundation of a new paradigm, or when a host of bad ideas generates one transformative one.