People who currently use powerpoint to be ineffective will find other ways to be ineffective without it. People also write terrible emails and create horrible documents. Ridiculous books are written. Zero-content instant messages are sent. Some people don't get how to use the phone. Shall we discard them all?
Those had their own limitations. But, yes, today's equivalent--whiteboarding--can be an effective communication tool for someone who knows and understands material having a discussion with a (preferably small) audience.
That said, I remember lots of transcription from a professor's notes to a blackboard to students' notebooks with very little value-add along the way.
