At least going back to the time of Kant, metaphysics is at the core of philosophy and still remains so. It is an inquiry into what reality, fundamentally, is; or what the basic structure of reality is in the highest sense. The bookends of metaphysics might be summed up as the rationalists at one end and the empiricists at the other. The rationalists believe that we can reach substantive conclusions about reality through reason, that is, ideas independent of all empirical experience. The empiricists, at the other end, don't think so. Reason, the empiricists believe, is limited. The only way to reach substantive conclusions about reality is by sensory experience, that is, by way of the natural sciences.
The problem as it stands before us is we are looking at this present reality before us through special spectacles which act as a kind of perceptual apparatus that alters the truly real. These spectacles even include Kant's space and time not to mention our senses and the empirical world. What we imagine to be the world or reality, really amounts to an image that has been altered by these spectacles. This leads to the conclusion that reality, as it is, with the spectacles removed, is not accessible to us. Thus, we only have access to how things appear through the spectacles. It is almost like we are trapped in Plato's cave which is described by Socrates in The Republic (531d).
We may speculate on what ultimate reality is by way of various concepts. But according to Kant we can't get beyond the limitation of reason and empiricism, or the same, remove the spectacles to see the noumenon. But if, according to Buddhism, the one who looks through the spectacles (the five skandhas) is not the spectacles, we can begin to dis-identify with the illusory world the spectacles create.
Our psychophysical body is the perceptual apparatus by which we see phenomena (objects of possible sensory experience) which act to conceal the noumenon, i.e., the thing-in-itself, including our very self (S., pratyâtma), which is enclosed by phenomena. This leads me to say that on the rationalist side of metaphysics we haven't gone far enough. Reason doesn't end with mathematics and logic or abstract thought. It possesses its own power to penetrate through the veils of the most subtle phenomena and setting all aside, come to self-realization.