It's an acquired taste, much like beer. I started with Death's Scream Bloody Gore in the late 80's, and I couldn't understand a single lyric to it at the time (and probably still can't). I would just filter out the voice and focus on the music. Then became completely oblivious to the voice in all death metal. I almost just listen to it as if it was just another instrument, rather than thinking of it as singing and lyrics these days. I couldn't tell you a single line in a death metal song and I probably have at least 30 albums from the genre.
What I like best about Death Metal. I find myself being able to do my job (software engineering) easier when I'm listening to it. Instead of actually listening to the song (which is a distraction) it helps filter out all the noise in the office around me so I can concentrate. Which is why I like it so much.