Beaten 46-14, it was Ireland's seventh quarterfinal loss at World Cups. They had also failed to build on their Grand Slam win of 2018, and their win over the All Blacks in Dublin. They had finished third in the Six Nations earlier in 2019 and had suffered a record 15-57 loss to England in their World Cup warm-up game.
"We haven't sat down and talked about it, ultimately we didn't do the basics well enough against New Zealand, but it'll be tough to live with," he said at the European Champions Cup launch in Cardiff this week.
As well as losing to the All Blacks, Ireland had also been beaten in pool play by Japan.
"We felt there was a lot more left in us. We got to where we wanted to get to, which was that quarterfinal. I know it was against New Zealand and not South Africa, but either of those games were going to be incredibly tough.
"We knew we had to produce our best performance to get past it and we didn't come close to it. They were excellent on the day, it's as simple as that," he said.
While there would be plenty of conspiracy theories and opinions on their performance the bottom line was the All Blacks were excellent, he said.
Sexton didn't hold with the view that coach Joe Schmidt's legacy would be tainted by the side's inability to progress.
"You just think about the success he's had, he has the best win percentage by a country mile.
"He's changed the expectations of Irish rugby, of Irish supporters. He did it in Leinster and did it again and if we had done what he asked of us in the quarterfinal, would we have won it?
"We'll never know because we didn't do it," he said.
"We should take the majority of the blame as players, but his legacy in the players' eyes will always be there," Sexton said.