I think that it’s pretty clear this is a case of force majeure, Virgin Voyages had intent on running the sailing program in Australia in the 24/25 summer and had published cruise itineraries.
I purchased an onboard “next cruise” voucher - a MNVV for those familiar with Virgin Voyages - on a cruise in the 23/24 season, with the intent of using it for another AU/NZ cruise.
Obviously the Australian cruise program for 24/25 was cancelled so I just sucked it up and booked something in the Caribbean. I’d paid $ for this voucher - those on the freebie aren’t out of pocket. They still have a voucher. It's not reasonable to expect VV/VA to pay for a flight to SJU, MIA, BCN, ATH etc. Air travel to the port of origin in Australia would not have been included anyway.
