The point of a genre is to group pieces of music that shares a certain characteristic. If you don’t like that specific characteristic, then the genre just isn’t for you.
That’s quite the over simplification when bands like Beherit and Iron Maiden have different styles of riffing, different types of production, different subject matters, vocal style etc. When talking about a genre like Metal you can’t lump music like that into one group because there are subgenres in subgenres and even bands who are in the same genre like Autopsy and Behemoth sound nothing alike.
Yes it’s a simplification but for some genres it can be applied. For very broad genres like metal, it may not hold, but then it applies to its subgenres. In fact, I don’t like different metal subgenres for different reasons, but ultimately, I wouldn’t say I like any subgenre, so it’s not wrong to say that I don’t like metal.