Metaphysics are your fundamental assumptions. These are chosen: they were chosen by you (although you probably weren't aware of choosing them, but just passively accepted them).
Fundamental assumptions are chosen - but they are not arbitrary; because the assumptions have consequences. You can choose whatever you want to believe - but sometimes you will not be able to make yourself live-by these chosen beliefs; and other times you will live by them (including thinking by them) such that they lead to nonsensical and therefore self-refuting outcomes.
The trouble is that in a world where people have stopped thinking- and when their assumptions lead to incoherent, nonsensical conclusions, instead of sorting-out their metaphysics - they just stop thinking (easier to do than ever before in human history - due to the ubiquity of mass media and social media).
Anyway - my point is that if you have certain (very common) assumptions, then you will either have a nihilistic, hope-less and despairing world view --- or else you will have to stop yourself thinking about anything serious.
There are innumerable commonly-held assumptions that lead to this: that Man has no free will, that the world is either random and unpredictable or else rigidly predetermined, that nothing exists except what has been described by 'science', that morality is a matter of opinion, that beauty is wholly in the eye of the beholder... oh, there are dozens of such.
Indeed, most of people's primary assumptions nowadays are of a type that lead to nonsensical or incoherent conclusions - so it is futile to complain about the low standard of rational public debate when rational debate is only possible on the basis that people are able and willing to examine and revise their assumptions when they lead to absurd outcomes.
Because perhaps the most absurd modern metaphysical assumption of all is that metaphysics is meaningless and all decisions should be made on the basis of 'evidence'!
Whereas (as quickly becomes apparent in any disagreement) unless there is agreement on metaphysical assumptions then the cannot even be agreement on what counts as evidence, leave aside the matter of evaluating the strength of evidence...