It's popular because it minimizes the amount of people who don't like it (aka you) and maximizes the people who do like it (aka everyone else).
Just because you don't like it for a particular reason doesn't mean others won't like it for that reason. Everyone has different likes and dislikes. The thing with Death Note and other popular anime is that they have something that stands out. For Death Note, it's the storyline, animation, and general conflict between geniuses, all combined together, that make it so popular. For other anime like Bleach or Naruto, it's the fact that it's shounen-or