I don't think McGree underperforms for Aus, JS.
I don't see him play at club level, but he is our best forward in terms of defensive duties.
He constantly positions himself well to be the second defender in optimum positions to support the wing backs, when Aus cedes the ball in the opposition Ball Possession phase of play.
McGree makes timely tackles, effects more frequent intercepts, and easily causes the most turnovers of the attacking line in data I've compiled. Of course he is more experienced than any of the current others - Metcalfe, Villupillay, Toure, Irank, Volpato, Yengi. And better at his defensive duties than the experienced Mabil and Hrustic.
I think this WC showed Toure, Irank, Volpato, to be a bit better than their attacking teammates in an offensive context. I suspect Toure was carrying an injury. Hence , Popa didn't play him as much as expected.
If McGree was at the WC, we could have had another superior attacking outlet for the the front 3.