Its not really an issue of the quality of the bands, its just that they don't fit in the genre. Like the nu metal bands, what about korn, or the deftones, or linkin park, or mudvayne, or crazytown was metal? There was distortion sure, but thats about as far as it goes. Bands like Slipknot have some metal influences but the whole detuned distorted riff thing is also an element of grunge, and most of these bands riff structures come more from grunge than from old school metal. Then you get the rock, hip hop and electronic influences that many of those bands brought in, and the metal influence i really on the backburner. I mean, the only thing metal that any of those bands had was the odd metal riff and the odd burst of double kick. AIC on the other hand for sure has a lot of sludgy parts and similarities can definitely be drawn to the old classic metal bands. For me, if AIC are a metal band, then where do you draw the line for hard rock? Their style of riffing is very much in line with the hard rock of the last 2 decades, Stanley's vocals were definitely grunge, the drum lines are thoroughly based in rock patterns, so the only metal element really is the sludgy feel. Another thing, members of bands say a lot of things. Trivium said that The Crusade would be "ridiculously technical thrash metal", while it was basically neither. Anyhow, AIC are on metal archives which means enough people see them as metal that it makes no difference.
ETID and Converge are definitely metalcore but to me at least are two of the highlights of that genre.
Wow that was kind of a waste of time writing all that out
Korn are pretty metal, it's that some people don't like the hip hop element there, but they've made it metal, Deftones I would agree are not as pure of a metal band like AIC, cause they have the vocalist who's really into the art/experimental rock, and the guitarist is a metal guy, so they have like two opposing styles, they def have some metal songs though, Linkin, well they aren't really metal at all, it's like they took the lightest parts of Filter, Korn, Deftones and made it pop, Mudvayne are fairly metal, no question, I don't know how you can listen to them and think that they are not, at least their 1st 3 records are, after that they did some more radio friendly stuff, Crazytown are prob more rock than metal.
The detuned guitar has been around at least since the Beatles did "Dear Prudence", Zeppelin used it a bit, as far as the influence on metal, it comes from Slayer when they started to use it, doom bands used it, then Death used it, hair metal bands used it too, Motley Crue doing it alot, not AIC, Swedish death metal, Tool, Pantera, Prong, Helmet and I'm pretty sure some other bands were also using it at this time too, so it's a Slayer thing, not a Washington State thing, now a lot of metal bands have used it since.
What is a grunge riff structure, cause AIC's riffs are pretty classic metal type riffs.
Staley was Staley, he wasn't a genre, he was unique, like Ozzy before him.
Classic metal drumming was based on rock/jazz, until Motorhead came along and changed metal drumming, doomy metal doesn't use fast kick drumming anyway.