Isn't it also that Black Sabbath's fanbase has grown in the last 50 years? You have hippies and Boomers that liked them in the 70s and 80s that still like them, and then every generation of metalheads and metal-adjacent fans also like them, so the number of potential buyers just keeps increasing.

Sabbath is one of those bands whose popularity never really dwindles, it only increases. Compare that to bands that were popular among Boomers and Gen X Metalheads (Saxon, Accept, Skid Row, Grim Reaper, etc) - their popularity is constantly declining.

Cattle Decapitation isn't quite 30 years old yet, but is getting there, and they definitely exploded into popularity with Monolith Of Inhumanity. To the point where nowadays they rarely perform any songs older than that record these days, and it seems like the bulk of their recent fanbase is okay with that. Unless I'm mistaken.

Yeah, I was going to mention these.

I think everything Katatonia has done in the last 15 years or so is way better than the classic death/doom stuff, and that's reflected in what the fans are interested in. Although I still think maybe The Great Cold Distance is the absolute peak in terms of fan favourites. Sorry, not sorry.

Paradise Lost, honestly same. The classics like Icon and Draconian Times are still great and seem like they're always popular live picks, but I don't know if I have any interest in returning to the first two albums, they just don't fit in much with their modern sound. I also kinda get the vibe that One Second might be the most popular album among the majority of listeners, though their newer material has been almost universally great too and probably brought on a ton of new fans.

I guess it's not quite "newer" anymore but I'd also say that Opeth is probably far more well known for Ghost Reveries and Watershed than anything else from their earlier catalog.

At this point I'd also say modern Amorphis has far eclipsed their early material's popularity, though I'm not sure if there's any one album I'd point at as being the biggest. It's almost hard for me to remember that at one point Tomi was the "new" vocalist and people felt like he had big shoes to fill after Pasi left... these days it feels like he's always been in the band and it'd be hard to recognize without him.

Amorphis is definitely known better for their modern stuff. Queen of Time and Red Cloud really solidified that. Karelian Isthmus and Thousand Lakes are amazing albums, but unfortunately they're just better at the progressive folk metal sound.

The one thing I will disagree with you on though is that Katatonia's new stuff is better. I love Great Cold Distance and some of their recent albums are pretty unique but I think they went too soft. That part about 3 min into Brave is one of the most haunting, heaviest bits of doom/death I've ever heard...and then they release things like Winter of Our Passing and it's basically pop rock.

Yes, this is a good point.

Only speaks to how timeless their music is.