Its just an opinion, they seem to have a revolving door policy. If they kept a core squad of players together and developed them they would be near the top of the cricket tree where they should be on talent.
NZ had this same problem of throwing players away after one of two bad series. When does it end. To be a consistently good cricket team you need continuity not a team which is in a constant state of flux. This is why Australia is the best consistently, they may be able to be upset now and then, but the players know they have the confidence of the selectors and aren't playing for their place every game.