From Helen Slater to Melissa Benoist, Supergirl has always been attractive, until now. Why would Gunn cast an uggo as the new Supergirl?

Helen Slater was smoking hot as Supergirl, but her replacement is uggo Milly Alcock. What did James Gunn mean by this?

>Helen Slater: hot
>Milly Alcock: ugly
What went wrong?