Why don't we have classical theatre in the 20th and 21st centuries

This is because of modern cinemas!

because of modern cinemas

Explanation:

At this edge of the early 21st century, we would call this a traditional theatre experience. It is familiar, not one of those experimental, avant garde productions. It's what we expect from our theater. Hasn't it always been like this?

It hasn't. This experience that we call theater is still relatively new. It is only about a hundred years old. Shakespeare would cry "foul and most unnatural murder" if he were to see it. Or, at the least find this new theater a novelty unlike what he did. Sophocles, Moliere and all of the great actors of the 19th century would have the same response. The theatre we call traditional is wildly divergent from what came before.

It could be said that theatre changed to reflect it's time. It became a more realistic and psychologically connected experience. And yet, we lost some vital aspects of theatre in the translation. I believe for theatre to meet the requirements of expressing what it is to live in the 21st Century and to remain vital, we need to go back and reclaim some of what made theatre theatre before the turn of the last century. [Read the post on The Rise of Realism]

Every time theatre has remade itself, it has begun by looking back at what came before. The early seed of the shift to realistic theatre began with a look back at Shakespearean production practices. The rise of the regional theatre movement in this country took a look back.

Let's compare the production of Shakespeare's Julius Caesar in the newly opened Globe Theater (1600) and the recent production of Tracy Letts' Pulitzer Prize winning play August: Osage County, (2008) [i]