What are the literary conventions that dominate the writings of the modern playwrights?

Modern playwrights' styles are varied, but some trends can
be found in their diverse work. Generally, modern drama is thought to have started with
Ibsen's A Doll's House. One trend found in modern drama that
certainly shows itself in A Doll's House is the idea that the
playwright leaves the meaning/motivation for actions open to interpretation. The
audience can speculate about Nora's true reasons for her decision, and things are not
left in a neat, tidy package at the conclusion of the play. Absurdest playwrights such
as Beckett, Shepard and Pinter who fall in the modern era take this "open to
interpretation" approach to another level, using circular structure and taking the focus
away from surface-level plot interpretation.

Another trend
can be seen in the breaking of stereotypes for, most notably, female characters. Ibsen,
Shaw, Churchill, Wilde, and Williams are all noted for standout
females.

The inclusion of humor also became more prevalent
in the modern era, especially looking at Oscar Wilde's intricate witty
dialogue.

Theaterpro.com describes the origins of modern
drama in this way:

Modern drama as we know it in the
twentieth and twenty-first century began when Nora slammed the door on her family in
Ibsen’s A Doll’s House. Together with Strindberg and Shaw, Ibsen swept away romantic
melodrama heavy with the passions of stereotypical heroes and heroines to create
dramatic works that presented real-life characters in action that reflected and
questioned prevailing morals and mores. Dialogue, once florid and poetic became sharp,
pointed, and often witty.