Gender identity is wayy to complex for a simple example and it's at least partially something natural.

Also I didn't say that something invented has to be real.

Even Dragons and Witches are real in their own context. They don't exist in this world but they exist in the world of the stories being told about them.

Biological sex is importantly distinct from gender, and biological sex is quite real and crucial to differentiate in a medical setting.

I work in biotech. I absolutely understand and agree that a person should be allowed to identify with whatever gender expression they want to.

But in a clinical context: no. Full stop. Biological - that is, chromosomal and unaltered phenotypic - sex is very often a crucial data point to understand when testing or treating a patient. It’s science. Chemistry and biology do not give a flying fuck about anyone’s feelings or sensibilities on gender identity.

Edit: as I hoped was very clearly evident from my comment, I am fully aware of the distinction between gender and biological sex. The only reason I even made the comment is because, even at the biotech I work with, sometimes people still conflate sex and gender. Lots of people cross it up all the time - intentionally or unintentionally.