Hard to say.

Raw, genuine expression with unrestrained creativity and passion that resonates with me, even the record with no vocals Jenny Death. DG is an outstanding band in a league of their own and watching MC Ride and Zach Hill perform is, I don't know, compelling, hypnotic. https://www.youtube.com/watch?v=2MHhLDCJ57E You see that kind of energy in extreme metal, which is probably why I like them.

Perhaps it's the aggression that everyone has inside them, everyone knows it and "speaks that language", that is to say bands like DG make music that "speaks the language of aggression" very well and depending on the person, it either resonates with them or it doesn't. It's not just anger of course, the music is fun, wild and groovy also.
It's probably as uncomplicated as that. Just combine aggression, high energy, unleashed creativity and you end up with DG.

>meaning
I don't know what it means, the lyrics are too sphinxlike, I haven't studied them but they speak of trauma IIRC; and to say that their music is cathartic only, that it "just makes you feel better" is to reduce it. By listening to their music and watching them perform, I can tell that Death Grips means a lot to Death Grips, that's one reason I've never shat on them like their entire fanbase apparently. You see someone pouring their soul out and your first instict is to make shitty jokes for youtube thumbs up. If that's all they're gonna get then by all means retire, your "fans" don't deserve you.