I don't quite understand what you're getting at with this comment? In metal and punk it's pretty cornerstone of the genre to be authentic, and in metal to value human skills (all the solo parts, fast playing). I've played and listened punk and metal my whole life, but will also enjoy early Lady Gaga, Eminem, Kendrick etc. celebrities because I recognize their authenticity and skills. Sabrina Carpenter and Drake go over my head because of blatant ghost writing and even though they have good tunes, I vomit retrospectively.
So what is AI bringing to the fans of these genres that the fans might value? Because it's not authenticity nor is it skills. What is the point you're trying to make?
I am saying on surface it might seem they should be the staunchest opponents and as I said the culture is "only cassette tape is real otherwise fuck off and die" but simultaneously its also one of the least image/player focused genres in some ways, what is being played is of much higher priority than who in specific is playing it.
Hmm I can think of various examples where the guitarist was changed and people dismiss the new guitarist. Take a look at Megadeth for example - every new solo guitarist gets compared to Marty Friedman even though he hasn't been in the band for 26 years. So a lot of it is player focused.
But your point also stands here, every new guitarist must play the solos as close to the original ones as possible, otherwise it's not the same experience. So on the music level "what" is of much higher priority still. But I wouldn't say it is as black and white as you make it out to be.
Some of course have a very unique style that seems very hard to replicate. Personally I haven't yet found a single band that manages to faithfully execute classic era Slayer. But there are countless bands today who make very good execution of norwegian black metal and swedish death metal.
Edit: And a lot of modern black metal for example doesn't even bother with stating who they are. Member lists are pseudonymous or anonymous. I think this "anti god" culture makes metal different from other genres in some ways.
Ok I'm not as up to date with modern black metal, that pseudonymity seems cool.
There's also upcoming math rock band Angine de Poitrine who are also anonymous https://www.youtube.com/watch?v=0Ssi-9wS1so . In these cases you can argue that the person doesn't matter but in my opinion it still does. There's a person inside that costume, who has made the decision to be anonymous as part of the whole experience. That's part of their expression.
Of course there's then bands like Ghost who have mainstreamed this too - the players wearing the costumes are usually just contract musicians and don't have anything to do with Tobias or the music other than playing for money. Good for them but f that, you are just a robot at that point.
There's anonymity/pseduonymity where we have a entity that does not do any performances and releases cassettes with members acknowledged as "M., K. and J." or even nothing and there is "anonymity/pseudonymity" where a band tries to use that as its own image (eg Kanonenfieber). Obviously I meant more like the former which is legitimately a music first person irrelevant presentation, but modern black metal is a wide spectrum, it has some of the most image conscious crap out there too, if anything I think its probably the most superficial and image focused of the main metal genres. It's just that anonymity hasn't historically been part of death metal culture that much but I feel its actual presentation is quite workman like in many ways.