Any G20 that can't reach consensus on condemning North Korea's nuclear weapon aspirations and provocative missile testing isn't worth the carbon burned to fly these people to meet.  These are smoke-and-mirror events, more about posturing and photo-ops than anything else.  Worse yet, they are an open invitation for professional protesters to escalate their violence.  

The politicization of the G20 (or G7, or the UN) has undermined its effectiveness.  The most effective kind of multilateralism is the kind which occurs when nobody is looking....the kind that happens in spite of our political leaders rather than because of them.