I have to pick up on the point some have made that these changes reward those Qantas flyers who are "loyal" at the expense of those who are leeching off cheaper oneworld fares to obtain status.
Let's take my Dad for example (Platinum for 15+ years). Around five years ago, my Dad would easily retain Platinum (and then some) on QF only due to it having a decent international network. He could get to Frankfurt before 8.50am in the morning. He could fly to Beijing on a Qantas aircraft. He could take an overnight flight to Hong Kong on Qantas and connect throughout Asia. Through the BA partnership he could fly Europe-Tokyo/Shanghai/Hong Kong/Bangkok/Singapore-Sydney. This used to allow him to kill multiple meetings in the one trip.
Over the years he had to change his flights over to airlines such as CX, because of QF network decisions. The QF/EK alternative to Frankfurt, as mentioned above, gets in at 8.50am - too late for Business. The QF flight numbered alternative to Beijing is a China Eastern codeshare operating via Nanjing (enough said really.......). There is only one flight per day to Hong Kong. However, in order to stay loyal to QF where possible, he leveraged on the oneworld partnership of airlines such as Cathay Pacific. And where Qantas was available as a viable alternative, like on domestic flights, to New Zealand, the USA, Manila etc. - he has stuck loyally to QF.
Now, because of QF own decisions network wise, he is left with an option that makes it unrewarding to stay with QF because he gets punished for flying partners that offered an alternative where QF could not. But this is a choice that is beyond any reasonable person's control, other than the incompetent decisions of Qantas management.
People flying oneworld partners are not leeches trying to get status cheaply and are not any less "loyal" to Qantas. I understand that QF cannot be all things to all people. I do not expect QF to fly everywhere. But in a world of airline partnerships, it is not unreasonable to expect to be rewarded for flying partner airlines that offer an alternative where your business cannot.