Yep agree its a shame that WCs have taken on so much prestige as to devalue achievements in between. The 96 and 05 series wins you mention are my non-WC pinnacles as well. Three test wins on the trot in SA, and a Lions win followed by a Grand Slam which featured two completely different starting XVs being rolled out in consecutive weekends.... to think that display of depth has been reduced to just a footnote because the team shat the bed two years later is a real shame.
That said, knockout pressure and the fact unlike a regular season, both hemispheres align their seasons to the event, allowing all teams to aim to peak at the event, make WCs what they are.
They certainly require a different mindset though and I think that's something Ireland perhaps hasn't yet grasped. There's lots to to analyse about how each team played, but for me, a key one was Sexton turning down kickable penalties. I get they backed themselves to convert the field position into tries, and that belief was entirely justified based on how they've converted those opportunities in the last couple seasons.
But 07 in particular taught the ABs a very painful lesson - pride cometh before the fall, never turn down points. Jordie taking a nudge from 50 out showed how well that lesson has been learnt.