He's likely ignorant, where I'm from all metal is labeled "death or black metal", when there's so much of a hint of a guitar. But then, for people who really dislike the genre, why expect of them the differences between the many kinds? I couldn't tell the differences between all the hiphop for shit myself (and I used to listten to rap). That's no reason to be rude about others' music taste though, so much of that in this topic.
I used to listen to just metal when I was in my teens, but I don't know, at some point I felt I'd heard it all and of course, I still enjoy it but I listen to it way less and I've switched to electronical music of various kinds instead. Fun fact is that I used to listen to rap when I was a kid.
But then I have a very broad music taste. That said, you cannot possibly compare metal and rock of today with what it was in the 70s or 80s, I love music from that time, Pink Floyd and all that, but just because music today is no longer as it was back then doesn't make it bad.
Music evolves, so do people, at some point they want something new - both the musicians and the audience. As a personal example, in the course of 20 years I went from rap -> metal/rock -> electronic music.
Have you actually taken a look at the top selling albums of all time? It's pretty dire.
The Backstreet Boys have sold over 130 million records over the breadth of their discography - you suggesting they're better than virtually 99% of artists out there?
Why does this silly commercial argument of records sold still persist?