off the top of my head, border, boon, jones, steve waugh, mark waugh, taylor, healy
OK, let's go through those one by one:
Border UIMM had no push at all, seems odd if he did. Nonetheless, his performances had been down against
top attacks (WI and SA) in the final phase of his career even though they were as good as ever against the rest.
Boon, although he scored 188 in his last 3 innings, had averaged less than 23 in his previous 25. There is no way he was performing.
Jones, although 31 years old, had done next to nothing of note between 1990/91 and 1992 when he was dropped. He made two big scores in dead games (a speciality of his) and also made a match double of 77 and 100* where he was apparently missed about 5 times. While replacing him with Stephen Waugh wasn't the wisest idea just before a massive series against West Indies, Jones could hardly moan too much at the axe.
Stephen Waugh was patently obviously not the batsman he'd once been. Against Test-class teams Waugh averaged less than 38 in his last 25 Tests.
Mark Waugh, well, he was probably the second-worst performed of the lot. He barely averaged 30 in his last 12 Tests.
Taylor retired of his own volition UIMM, after a very poor final series.
Healy, well, jeesh, he was comfortably the worst. He averaged 15.20 in his last 13 Tests, and this would've been barely out of single-figures but for England dropping two simple catches.
Australian selectors may have been poor in the last 20 years, but none of the above were among any serious errors.