What makes a "good writer"

A good writer is the good mixture of writing skills and good content.
A genius for example was Oscar Wilde.
He knew about human nature, about life, about literature and knew how to write it.
That makes him unique and sublime.

You can have "good writing skills" but not knowing what to write, and you can have a lot of good ideas and not knowing how to present them.
That is life and that is why perfection is something so valued, because it is terribly rare...