Most honest post I've seen for a while. I share both your confusion and your "culpability" (for want of a better word).
Oh dear. You've been seduced - although I hope not - into The Great Wallabies Player Selections Myth.
Our Wallabies-level problem is not essentially about 'really hard selections dilemmas and new vs old players and so on' at all.
Our problem is that we have a Wallaby HC whom is a very good team motivator, quite good culture-builder, good individual player counsellor and guider, but who has totally failed to design and select a world-class national coaching team of the breadth and depth needed to compete with a other elite coaching groups with the best teams, or even some so-called Tier 2 teams like Scotland.
Grey's best days are super-obviously gone, Larkham's best achievement with the Brumbies is actually very good defence (credit Ryan there to a considerable degree for that btw) and certainly not attack. And so on.
And that neither of these absolutely critical positions/persons have had to undergo a performance assessment/results-delivered hurdle of any kind before becoming full-time Wallaby coaches 'because they just wanted to become full-time'. That is unforgivably lazy and indulgent.
We can ruminate all we like re 'selections' as though this game of numbers and new faces conundrum will unlock another set of Wallaby glory days, but the effort will be in vain until the whole Wallaby support coaching team (I'm still OK with MC as HC btw) is turned over and significantly upgraded.