I feel like playing devil's advocate here is a powder keg, but I think it's a little misguided to assume that the characters themselves would be inherently more black or something if they were voiced by a black VA. It wouldn't change the fact that these characters were conceptualised by Andrew Hussie, a white man, in 2009.

And that's not an argument for authorial intent, its just the reality of what these characters are. Simply casting a black person to voice Dave Strider wouldn't fix the problem. To me that's like making a Friends animated series and casting a black man to voice Chandler, as if that fixes the diversity issue. Dave is still archetypally white.

And that introduces a whole other bag of snakes. Say you actually want to reimagine the kids to be less racially homogeneous. The two credited writers for this project are both white, and one of them is Andrew Hussie. I have no reason to believe he's gotten better at writing non-white characters in the years since Homestuck. How do you figure these people would go about making Dave "black-coded", or Jade a Pacific islander? Would you relate to a black character written by Andrew Hussie?

I don't have a problem with people interpreting the cast of Homestuck as nonwhite, for the record. But it's always been something done in spite of the source material, not facilitated by it. Homestuck isn't good representation just by virtue of death of the author, its problems are too foundational.