It's not even the fact that Ireland have failed again to reach a semi-final.
It's the realisation that they never give themselves a proper shot at it.
This was the fourth consecutive World Cup knockout match lost before they had a chance to win it. They trailed France 27-0 at half-time in 2003, conceded a Shane Williams try, and all the momentum, to Wales in 2011 and then trailed Argentina 20-3 after just 22 minutes in Cardiff four years ago.
Different players, coaches, opponents and eras. Same regrets.
This seven-try shellacking was probably the worst of the lot given the team's experience, their record in beating all-comers in the last four-year cycle, the standard of the coaching staff and the absolute focus on avoiding the mistakes of 2015 by deepening the squad's depth.
All that, and for this? A 46-14 whooping?
There is no casualty list to explain it. Bundee Aki and Sean Cronin were unavailable here but the former's form was poor in Japan and the latter was out of favour and at the back of the queue as hooker behind the captain Rory Best and Niall Scannell. No, this was as good as it gets in rugby for a team facing its Everest.
They never came close to scaling it. Ireland didn't even make it to the foothills. They slipped a disc in their back putting on their hiking boots. Their first attack of any note or intensity didn't come until the first-half had lapsed into injury-time and it ended with Peter O'Mahony conceding a needless penalty.
Robbie Henshaw's inability to touch down for a simple try 67 minutes in was the entire tournament in a nutshell. Their entire year, actually. They were 22-0 down at the interval here and still trying to get the basics right. You couldn't help but think of the 60-0 in Hamilton back in 2012. Ireland were that bad.
How ironic it has been that a side famed for its mastery of the ABCs should be undone by a maddening inability to put one foot in front of another without tripping itself up. The sad fact of it is that Ireland were appalling almost every time they tried to use the ball. Missed passes, dropped balls and even loose kicks from Jonathan Sexton combined to cripple them.
Bon Jovi's 'Livin' On A Prayer' was belted out at half-time and it was achingly appropriate.
The hope was that Ireland had turned enough of a corner with the defeat of Samoa in Fukuoka but there were strains of the same virus that infected them here that were evident on that night too. Carelessness is a killer in elite sport and Ireland have been unable to rid themselves of it throughout a calendar year which went from bad to worse to unmitigated disaster.
You can say that this loss and the manner of it can't take away from everything Joe Schmidt and his team achieved over the course of almost seven years, but the fact that such an argument is even necessary now is an admittance that there will an asterisks beside this team, the coach and the era now that and that is a shame.
There was a piece written in the Kiwi press last week in which Ireland's defeat of the All Blacks last November was framed in the context of a jaded visiting side, that poorly selected and given the wrong set of instructions by the coaching staff. The inference was clear: Ireland only won because of what the world champions did wrong.
That's a harder take to tackle now.
The All Blacks were brilliant. Are brilliant. Schmidt put it well during the week when he said that plenty of teams have done pretty much everything right at times against them and still lost. You could accept that. This was always a huge ask for Ireland and coming back from it won't be easy for Andy Farrell as he moves into Schmidt's office.
He at least has the opportunity to rinse this from his hair. For Schmidt it is an incredibly disappointing end to nearly a decade of great times in Ireland. Ten of the squad here are already into their thirties and most of them are unlikely to be playing an active part when the tournament pitches up in France in 2023.
Rory Best won't even have the chance to flush this from his system with another game of rugby. Like Keith Wood after that hammering by the French 16 years ago, he has to walk away from the game on the sourest of notes. The speed at which this team's form and fortunes have plummeted has been astonishing.
Weren't days like these supposed to be a thing of the past?