All flights on the kangaroo route have to stop anyway. So Asians carriers, anything from Emirates and Qatar to Singapore and Malaysia airlines can offer the same route and then some. For example, BA and Qantas would mean you have to fly LHR-SYD, Emirates could offer you EDI-SYD or MAN-MEL, and you still have the same number of take-off landings - ie similar flight time but far more flexible. Add in lower labour costs etc, and it's no wonder BA was the last Western European airline to fly to Australia.
It's more nuanced even than that. The point about the hub-and-spoke model is that operating costs are minimised when the company is based at the hub.
British Airways has strong business between the US and India, for example, because London sits between the two, and their fleet is able to operate non-stop to both. Singapore Airlines, Cathay Pacific, Thai Airways, Malaysia Airlines and, originally though to a lesser extent Garuda Indonesia, appreciated their position between Europe and Australasia, as well as further East Asia. The Emiratis of Dubai identified that they too could act as a bridgehead between Europe and Asia Pacific, and also between the USA and APac. They were closely followed by their Emirati neighbours in Abu Dhabi, and then the State of Qatar.
Although Singapore, Hong Kong, Thailand, Malaysia, Jakarta, Dubai, Abu Dhabi & Qatar enjoy lower employment costs (and employment rights), even if they were subject to the same costs and responsibilities as European carriers, they'd still enjoy certain advantages between (say) Europe and (say) Australasia, based purely on geography.
So, to circle back to the British Airways example of the Sydney route, the route may viable based on one flight a day each way, based on 777-300ER operation, with 'Mixed Fleet' crew and the cargo demand. However, the aircraft that leaves London on Day One does not return until Day Five. The cabin crew don't return until (IIRC) Day Seven and the Flight Crew aren't back until Day Eight. During this time, they all have allowances plus hotel costs. They're then not available for duty for another two calendar days.
This is vastly more costly in all regards as they're based at one end of the route, rather than in the middle.
However, if you then look at the Qantas non-stop strategy, the economics change again. This is particularly the case with flight crew, who can't help but find themselves in London the 'day' after they leave Perth. And, as in the other direction, they don't incur any hotel or allowance costs en route.