Are the female characters in King Lear not realistically portrayed women but, instead, caricatures of good and evil?

While one hesitates to call any Shakespeare character a "caricature," this is an interesting question to consider. I would never call Cordelia a caricature, as she is a fully developed character, but I can see elements of caricature in Goneril and Regan, the evil sisters. They are not simply caricatures, but they come closer to that role than Cordelia.

At the beginning of the play, Shakespeare makes clear that Cordelia's frustration with her sisters' over-the-top flattery of their father leads her to moderate her own comments to him. When asked to declare her love for her father, Cordelia responds genuinely, telling her father she loves him but feeling it would make her dirty to use the false flattery her sisters use. Cordelia is so disgusted with her sisters that she refuses to mimic their behavior, a very human response.

In contrast, we don't get much psychological explanation as to why Goneril and Regan behave as they do. We tend to group them together as an undifferentiated twosome (look at online character analyses of the two and you find them yoked: Goneril-and-Regan), which suggests they are less than fully-developed characters.

At least initially, however, there's some psychological justification for Goneril and Regan's desire to curtail Lear, repulsed as we may be by how stunningly quickly they, especially Goneril, turn from words of utter devotion to rude cruelty that seems unnecessarily harsh and humiliating. In the sisters' defense, Lear does behave erratically and with poor judgment in banning Cordelia and Kent from the kingdom. He does come across as capricious and possibly senile. His truth-telling Fool even tells him he is behaving foolishly.

When Goneril and Regan lock their father out of the castle in Act II, scene 2, they have adopted a level of cruelty that does arguably border on caricature because it is not justified by what Lear has done. If we put this play together with Macbeth as joint commentaries on women behaving with ruthless cruelty to achieve their aims, you could argue that it is cruel behavior itself that becomes a crude caricature of wise power and that Shakespeare wants his audiences to see it that way.