What's wrong with the standard definition?
Metaphysics is a branch of philosophy that studies the fundamental nature of reality. It includes the first principles of being, identity, change, space and time, cause and effect, necessity, actuality, and possibility.
From that definition I think everyone has a metaphysical outlook on reality.
It's not only about evidence, but what can be inferred from evidence beyond the behaviours, and properties of the evidence. Even a hard core physicalist who sees nothing beyond what evidence reveals in and of itself, they are still doing metaphysics.