The iconography is so against her. The myth of Medea is of a screeching, vengeful creature. Think of when we did Hedda Gabler and how we discovered that the essence of Hedda was that she was a coward, a weak woman. We had to break through 100 years of performance history and the desire of so many actresses to play strong female roles. Here it is even harder.
Audiences can identify with weakness.
I think the Greek playwrights knew that. That they could entice the audience into an emotional debate about failure and dealing with being a failed person. What's so surprising is that we are surprised by that. It leads back to our misplaced image of Medea as a strong, wilful, witchy woman who slaughters her children. In fact she spends the play struggling to find the strength to do the deed.