Whatever's on wikipedia doesn't matter, metal subgenres are decided by the metal community. They are on metal archives anyways, but there's barely any metal to their sound. They are primarily a grunge band. They definitely don't transition into anything like the modern era of metal, they have influences from the classics though like Sabbath.
Look, just cause you only listen to black/death metal does not mean that AIC aren't metal, who gives a fuck about sub genres, if you hear it and it has the spirit of metal, then it's metal, AIC are clearly rooted in classic metal, if you don't think their records have a metal vibe, then I don't know what to say, grunge is just the 90's word for what Sabbath, Motorhead and Zeppelin sounded like then, it's just a marketing ploy, not a genre, they broke quite a bit of new ground for metal, you say that black metal is far more interesting, well I could say to you that it's the least interesting metal genre, most BM is probably worse than punk when it comes to musicianship, in that sense it's anti metal, cause true metal is about really good music, not just putting on some atmosphere and spectacle to talk about Satan, plus it's all about the same subject pretty much, I see BM more as performance art, a message and what the pagan religion does than music, cause really, if the Christian religion had not taken over Norway, would there even be BM, I think not.