I hear that, and you're echoing what Lopez wrote. What I am saying is that it is reductive to say that a play with people of color in it MUST be seen as a play about race. Likewise, it's rather blinkered to presume that a play with all white leads ISN'T a play about race by the very nature of its whiteness.
And it must be said again that white writers are regularly critiqued for writing all white plays.