Maybe at that hour a lot of callbabks didn't get answered.

It would be helpful if everyone that didn't have immediate need for a resolution would wait. Eventually, in most cases, the changes will be processed and your new itinerary viewable online. Even though changed you are not obligated to accept it.

Of course the wait times will be extended when a bulk change is affecting so many itineraries at once. Reroutes take time too so the average call time to resolution grows and makes it worse.

You should try working in a 911 call centre when a forest fire breaks out and is burning down a mountain into a residential subdivision in the middle of a city and lapping at the backdoor of a school. Try answering a hundred calls a minute and every call needs to be answered in case there is an unrealted emergency in the mix.

Does a schedule change or cancellation on an itinerary 6 weeks from now really require immediate attention? I had an LAX-OGG non-stop turn into a one-stop via SEA that was at least 6 weeks out. Subsequently, the flight times changed again. I didn't bother with it and the system ultimately cleared.

Monthly schedule changes are a thing now, we can't do much about that; in time, stability will prevail. Generally, excessive hold times used to be mostly weather related and imminent. These are not normal times. In February 2020, I had a paid PE fare on CX, I had flown the outbound in January and needed to reschedule the return as I couldn't transit HKG. I tried calling for days and messaged as well to no avail. Ultimately, I no-showed for the flight. When I later was able to contact CX, they rescheduled me without question and without fee. When the reschedule didn't work, CX refunded the unused segments.

As much as I love hurling through the air at 500 MPH in a cylindrical metal tube at 35,000 feet when I am Flying for Fun, I don't get bent out of shape if it doesn't work out quite as expected.

For, you, please buy a lottery ticket today, 10 minutes is impressive!

James