The Wallabies had lost 39-37 at home last week in dramatic fashion, but there was a far wider margin on Saturday.
The All Blacks were 17-0 ahead at half-time of the Rugby Championship clash after a pair of early Australia yellow cards and never looked likely to cede that comfortable advantage as they ran out 40-14 winners at Eden Park.
"That's a very disappointing outcome for us," Slipper said.
"We wanted to come here and perform; we were really gutted with the result last week, and we had a lot of confidence coming in, but the ABs were too good, clearly."
He added: "I'm just gutted the way we performed. It just wasn't good enough."
Coach Dave Rennie bemoaned "way too soft penalties" on top of the early trips to the sin bin for both Jed Holloway and Dave Porecki.
Analysing the match, he said: "We got shaded everywhere, didn't we?
"I thought the All Blacks' defence was excellent; we had enough ball at times to find a way through and didn't.
"We didn't defend well enough, and you can't give a side like the All Blacks that much time and space. They're good enough to hurt us."