Altman and kIESLOWSKI are formative. I have to say I've seen quite a few of Gaspar Noe's films. And Irreversible was the SUBTLEST film he's ever made.
Noe's movies have a dream like quality, I grant you, but much of that hides what as best is something that is beyond hard core pornography. There are some European filmmakers who have leaned into this - Catherine Breillat for one - but Noe is the Russ Meyer of European exploitaiton. I'll be honest, I've seen actuall pornography that's subtler that some of this films.
Still four out of five.