I think it depends on the circumstances of the traveller.
If it is an Australian who has been stuck overseas, then no problem at all as long as they have somewhere to quarantine.
If it is an Australian who has left the country to visit family/friends/be a tourist, and then returns home to Aus, also likely not to be a huge problem assuming they have somewhere suitable to quarantine, and can get enough time off work if they can't WFH during the quarantine period.
If it is an Australian who leaves and returns for work travel, not likely to be any sort of problem as their employer will have to wear the quarantine time.
If it is an international tourist, looking for somewhere to spend their limited holiday break, then I can see any form of quarantine, and even testing requirements, being enough for people to decide to give Australia a miss. Especially if there is added uncertainty that they could get locked into or out of a state due to a short notice border slam. That could ruin the holiday, or even result in missing their flight back home.