alt Hacker NewsHmm 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.