Australia don't pick players on age or "gut" as a policy. They pick on performance irrespective of age. Handscomb and Bancroft got their spots because they performed at the critical moment, not because the selectors "saw something in them". Accordingly they'll get dropped if they don't perform, as happened to the younger Martyn, Hayden and Langer and has happened to Handscomb while Bancroft is teetering. Its happened to both Marshes. Whereas a gut pick like Maddinson exploded in their faces. They probably gut picked Paine too. But he worked, possibly because he is more mature and his skill as a keeper is known. It seems our fc class comp does favour producing more mature players bcos it works over young players until they develop the skill to survive then prosper. They are usually approaching their 30s when that happens.
You could say Jhye Richardson is a gut pick but there'll be less pressure on him bcos, all things being equal, he'll be a squad member instead of in the test team. So he can be groomed rather than be expected to perform. But overall the fc system seems to favour experienced and older players and gut picks are a sign of desperation on the part of selectors.
In general agree that Aus tends to be able to, and does, pick proven players, so does SA when given an opportunity. However it depends on the state of the team as well; my original point was that Aus had a fantastic team during the late 90`s into the 2000's with lots of depth at the FC level. It is quite clearly not the same today and when Aus has struggled, they have picked a few players on 'potential' rather than outright proven ability and scores, because there is no obvious replacement just waiting to come off the ranks (hence the Marshes),... that is when teams do look at talented youngsters that may fill a role. Of course any player needs to have put up some scores and shown something before getting selected.
Specific to SA's problem is that we need a decent batting allrounder and none of the current players are putting up their hands (however weak the FC system is) nobody is outright doing more than everybody else. So we have ended up picking Morris (who is erratic) and Phehlukwayo (who has potential but also for non-cricketing reasons is being picked, and is more a LO player), but I am advocating for Mulder, who is just 20 has put some good performances in and has a lot of ability; if there was a 30 year old player that was playing out of his skin that would be easy pick. There is not such a player in SA at the moment.
If SA go for a 7/4 split, with injuries to the first choice replacement, Bavuma, and an injury cloud over Faf, do you bring in a 30ish age batsman as a replacement that has had a single goodish season but not shown much else, and will probably play a maximum of 2 tests before the first choices come back; if he was a batsmen who had been scoring lots of runs for 2 or 3 seasons that was just unlucky not to be able to replace the incumbents then he would be an easy choice.... not what we are talking about here. Or do you go for a 6/5 split and play the extra bowler/erratic allrounder or do you consider the highly talented youngster that has scored runs and been taking wickets, but still unproven.... so making a 'gut' call and sometimes just going for an unproven because there is no obvious better choice? And every team and selection panel has done that at some stage, sometimes it has worked, sometimes not.
