Well someone used JFK as an example of one of the busiest airports in the world. Wikipedia shows the annual movement rate there is 410,000. They have two sets of parallel runways. Now compare that to Brisbane, which except under relatively rare circumstances is primarily a single runway operation with 226,000 movements in the last year. Now it should be easy to see that per runway Brisbane is moving more traffic than JFK and explain why you very rarely get no delaying action.