It wasn't a lack of support runners actually.
2 examples stuck out in my mind in the game. The first one was Simmons took the ball near the try line. He had Coleman and Mumm as support runners. As soon as Simmons got the ball he was tackled, and as he had no momentum he was driven back. Both Coleman and Mumm overshot and ran straight past him rather than latching, or driving on the tacklers.
Coleman attempted to double back but unfortunately it was too late.
Another was Hooper having Moore and another in support late in the game. He made a half break but was mowed down. The support dropped off completely due to him making an extra 5 meters and were not there in time to secure possession.
The support is there but it's seemingly not smart enough, and not aware of the ball runner enough to make the right decisions and put themselves in the right position. I'd wager there are examples of this for every single player during the game which makes me think it's a coaching issue.
It was sometimes, and, to be honest, if the support runners are there (and they were not always) but miss the cleanout or do it totally ineffectively, that is lack of support for the ball runner.
But you're right in that the execution of the support play is poor. Coaches have to take the rap, but seriously, if a lock / back rower at this level doesn't know how to clean out with some effect, that also reflects poorly on the player. Really no excuse for players at the top level being so inaccurate.