I'm not sure it's a case of these iconic directors declining on a skill, talent, or creative level, i think it's more them reaching a plateau and never proceeding any further.
3 Mothers was not evidence of Argento losing his touch in any way, it was him still stuck in the 80s, if i didn't know any better i would have thought it was made in the 80s, from the lighting, to the acting, to the cinematography, to the gore effects, it was a pure 80s film.
That's the problem for some, they can't accept the fact that Argento is not going to fall in line with modern day cinema, he's still inspired by the past and he has no compulsion or desire to modernize.
Now if you loved his 70s/80s output like i do you won't have a problem with his output from 2000 on because it's a flashback of sorts, to me that's a great thing, a legend working in his own creative vacuum of sorts.
It's expectations, i don't expect him to emulate anything conventional or to try to outhip the crop of new hotshot horror directors on the scene, he never did that before and he's not going to be starting now. Personally that's where i think Carpenter went wrong, he tried to be something he wasn't
Argento is still one of the best horror directors working today, even if his output post Opera has never reached the lofty heights he once touched effortlessly almost everytime.
We changed, the world changed, what we expect from horror has changed ( for some ), we expected him to change also, but he never did and i'm grateful for that. I appreciate the continuity of his creative impulses
Can't wait for Dracula 3D, should be an 80s cheesefest of the highest order.
Watching any new Argento film now is akin to taking a stroll down golden age of horror lane without the winking at the camera conceits because he's not trying to recreate that period he's still living in it mentally and as one of it's major contributors he has an intimate knowledge of it unlike some knowing reference geek who may not have even been born when Suspiria came out.
If you skew towards modern horror then don't bother trying to get Argento, you'll get frustrated but if you have some patience and are a bit adventurous i recommend any one of his films, even his slight misfire that was his wild take on Phantom of the Opera, what a surreal mess that was
Only one that disappointed me was Cat O 9 Tales, way too many silly visual effects and not enough compelling atmosphere