I agree that this is basically an insane discussion.
One can always draw trees of connections between art forms and claim similarities and so on. The people who would discount a new genre's achievements by saying 'it's nothing new, it's just the same as XXXX' are only interested in displaying their own imagined knowledge and rhetorical ability. What do we gain by agreeing or disagreeing that grime is the same as hiphop? It's like having an epic debate and finally concluding that apples are the same as oranges, both being fruits, growing on trees etc. Why do we need to ignore difference, simplify, homogenize? Can't we enjoy watching everything splinter off into more strange niches and sub-developments? Personally it's what keeps me interested.
Hiphop has turned into a commercial behemoth and now must address those needs as well as it's own goals. Grime is delightfully unencumbered by that, yet. That's one of the things that makes it exciting to me. You know that Juelz Santana could/would not put Ice Rink on his LP or even his mixtape now, because it's just too different, and he has something to lose. The fact that Grime is still underground, still poor, still disorganized and full of criminality means that the pure sound of the music and of the lyrics is still more important than how many units it can shift, because it better be since it's not gonna sell more than a few thousand white labels anyway. That, I believe, will change. Even drum n bass, to my ears, bent towards commercialism, homogeneity the same boom chak beat after a few years, even though nobody ever got really rich. I hope the same wont happen with grime but it probably will, and then the people who get tired of that will splinter again and the process will continue. Of course you can't ignore the connections between something like hiphop and grime completely but one MAJOR difference between them is that hiphop is more than 20 years old now and has become a global pop music.
This brings me to another of my pet peeves lately, the concentrated hype-attention on grime and the pressure for some kind of 'results' to equal that inflated hype. If you want to compare to hiphop it took two decades and a LOT of change, figuring out, aesthetic wars, etc to get to it's current place. Be patient please, un-realistically high expectations and the resulting backlash may do more damage than people care to imagine, that is for those who care at all.