Well QF certainly aren't alone in that regard, but you and your family do seem to have had an inordinately poor run of this happening. Hope it gets better (on whatever airline you choose).
This is my Etihad experience. Four years ago I booked myself and two other family members F class from AUH to DUS.
After our flights have been ticketed for several months, Etihad pulled out of the AUH-DUS route and moved us to Air Berlin's J cabin.
For those who don't know, four year sago when Air Berlin became Etihad's strategic partner, they had only just moved from being a low cost European charter carrier to the full service airline league, which meant their J cabin was equivalent to the international PE, at best.
I objected and proposed a move to Etihad operated service AUH-FRA (absorbing travel between FRA and DUS at MY COST). Etihad declined and we continued to argue to teh point of exhaustion.
Several months later (whilst still arguing) they changed a/c type on the route AUH-FRA to Y/J configuration only. I even accepted downgrade from Etihad F to Etihad J, but would not accept Air Berlin's 'supposed' J cabin. Etihad declined again!
We ended up in a lock down and with 2 days spare before travel (with no other options options available to me at that late stage), I begrudgingly accepted on a compromise, i.e. stand-by in Etihad J from AUH to FRA, subject to availability on the day of ops. It turned out J cabin was available at the time of check-in and we flew in J cabin from AUH to FRA.
Compensation for downgrade from confirmed F to stand-by J had not come willingly and over many arguments with several (useless) layers of management within their Guest Relations department, we received a token amount of Etihad Guest miles.
Not that it should matter, but I held Gold Etihad Guest status at the time of that mistreatment.
Four years later my anger had subsided and recently, I booked myself BNE-AUH in F, returning AUH to SYD in J. Return flight was a completely mismanaged debacle from start to finish, and I missed my domestic connection from SYD to BNE, which was booked on separate ticket with QF, resulting in an overnight stay in SYD at my expense.
I used this opportunity to test the progress Etihad had made in the last four years in the space of GENUINE care and accountability for personal shortfalls by writing in to them and explaining the situation. I received a template response, lecturing me on terms and conditions of carriage, paying general lip service about how they hope to do better next time ... AND (wait for this) ... inviting me to join their Eitihad Guest Loyalty Program !!!
That was at the time when I was still Etihad Guest Gold member (although through flying Etihad partners, not Etihad itself), which was evident from my boarding passes, my travel itinerary, Etihad's internal databases such as electronic booking/reservation file, passenger manifest, not to mention all my correspondence with their Guest Relations department, including return correspondence from the Etihad's dedicated Gold member email address.
I accept things will go wrong when leaving to humans to be in charge, but my philosophy is to judge the airline by their ability to recover from the bad situation. In my experience, Etihad had proven cultural inability to recover from the unjust treatment of their passengers (guests), because there is no genuine intent and genuine care behind their service promise.
Following this last insult, and after I explained my feelings to Etihad in no uncertain terms, they put an abrupt stop to communication, and thus, five month after this latest incident, the matter remains unresolved and ignored on part of Etihad. However badly Qantas may have behaved towards the colleague traveller, I would take them over Etihad any time.
