Coach Les Kiss called Australia's performance "unacceptable" after they crashed 43-21 to New Zealand on Saturday but said there was time to improve before their home World Cup.
After a 50-19 thrashing in Auckland last week, Kiss was hoping his young side would bounce back in Sydney, but they were routed in a devastating first-half.
They conceded three tries in the opening 20 minutes and six in the first 40.
"Look, it's unacceptable, 22 points like that, and you put yourself on the back foot, and the boys know that," he told Stan Sport.
"It's just not on. You can't do that. We've had two bad halves now in the last two weeks, and it hurts you."
The All Blacks tore the Wallabies defence to pieces, undoing a lot of the improvements seen since Kiss took over in July.
He had enjoyed five wins and a draw from his first six Tests before coming face-to-face with the All Blacks juggernaut.
Australia were missing some key players including fly-halves Carter Gordon and Ben Donaldson, and influential centre Len Ikitau, but it was nevertheless a sobering lesson a year out from the World Cup.
"You know a lot of young guys, single Test numbers, learned a lot tonight for sure," said Kiss.
"But as a team I think there's got to be a little bit more thinking about what it really means to actually turn up in that first-half and make sure we don't make those errors that we did.
"We could have scored three times but we just didn't work hard enough to get around the corner to score those tries. So there's little things there that are just hurting us."
Australia now head to Europe for the Nations Championship, with Kiss set to name his squad next week, which will be key as the build-up to the 2027 World Cup on home soil gathers pace.
He has a slew of veterans who have put their hand up to make international returns, including James Slipper, Kurtley Beale, James O'Connor and Bernard Foley.
Whether he picks them remains to be seen.
"I would still be optimistic for sure. There's some guys that we don't have here, out of choice, some experienced guys," he said.
"I've got to make decisions. I've got to make an eye on the future a little bit but also make sure we win the Tests in front of us."