deeptheres only so many ways to discribe slumping man or describing the hardship of life over a beat. Everyone sounds like a rebore of a rebore. Members of the square say "bet you thought i was gunna say..." like say Merky Ace wasn't spraying those bars in 2011.
UKHH or Road Rap or w/e took the violence and spun it off into a much darker grittier genre, look at the 67k videos for example and i think that sole a lot of grimes fanbase. Rappers like K Koke and DVS did the roadside struggle songs better than grime artists with few exceptions (Dot Rotton being an example of that)
an obsession with professionalism in a genre infamous for lacking any also doesn't help. Grime used to be unplayable in clubs and the police tried hard to lock it off, and it was killing the scene. But it's easy to blame the police and say the government shut down grime but MC's acted the way they did; getting rushed on radio happened and it drove off major investers. MC's had to soften thier sounds to get acceptance and thats contributed to it. Fans might have liked the rawness of the Grime scene but labels didn't, and ultimately too many people pirating music ate up any chance of financial success of going without a label.
So MC's had to adapt to the police strangling the scene and poor consumer sales and the result was a softening of the sound.
just my two cents i could be wrong.