It has been now many years ( from memory they ceased in about 2012) since Cathay offered 1st class to Australia.
It ceased because there was not sufficient demand on the route and I suspect that this has not changed.

Brisbane -CX is using the B777-300 as opposed to the A350 to Brisbane very much due to the high perishable freight demand .
The 777-300 can take up to 50 tons of belly freight as opposed to A350's 16 tons
CX also currently has a weekly dedicated B747 freighter flight to Brisbane