I would submit that the very idea of "nature", as used informally, is ill-defined and frankly incoherent, and should not be used, or at least should only be used loosely within specific contexts where it does make sense (a healthy ecosystem in which human beings also thrive, which is no doubt a range), like "I love taking walks in nature". What is natural under this definition? If water from a stream natural, but is water synthesized from hydrogen and oxygen unnatural?

The only sensible definition I know of of "natural" is "according to the nature of a thing". Thus, human beings have a nature, and that nature is what determines what is good or bad for us. Arsenic isn't poisonous as such, but it is poisonous to us by virtue of our nature. We are rational animals by nature. And so, unnatural are things which depart from that nature, like the desire to eat glass or having a sexual interest in oak trees and so on. It is the nature of a thing that is the reference point that allows pathologies to be defined. By nature, we should have two arms, hence to lose or lack an arm is a defect. Similarly, psychological disorders only make sense with reference to the normative, which is defined by human nature. To say "everything is natural" renders the word meaningless, annihilating all justifiable and objectively normative statements, which is absurd. If everything is "natural", then nothing is unnatural, because natural is simply identical with everything.