Writing and Rewriting and Rewriting

Listen to what Alex Epstein offers in his blog Complications Ensue: The Crafty TV and Screenwriting Blog:

"I don’t think you need to read any more books. I think you just need to write more scripts. Looking back on all my scripts, the first feature spec I’m still willing to show people comes in around #15 or so. It takes a while to learn how to write screenplays.”
“The key to becoming a better writer is writing, and rewriting, and rewriting, for years. Do you think people would get paid so much if it was easy to learn how to do it?”

Can it be any more simply explained than that?