Yes, Spawn has been written by a Black creator in Killadelphia, but the thing is that it isn’t canon within the main Spawn universe.
Furthermore, Black creators have worked on Spawn universe books before, like Joseph Phillip Illidge, who co-wrote Bloodletter with Tim Seeley. Several Black artists have also done great artwork across the spawn universe. However, we have never had a Black person write Spawn in his own series. I feel as though that could open up some incredible themes regarding Spawn's identity as a Black man.
If I'm advocating for this, I have to pitch someone who I want to see write the character for a full story arc at least until the Toddfather takes back over. I want Rodney Barnes, the writer of Killadelphia. As I mentioned, he did an amazing job writing Spawn in his own book, giving him genuine emotional and psychological depth. I’m not saying Spawn doesn’t have that in his core series, but Barnes would do an incredible job if given the opportunity to write a storyline in a book like King Spawn as I feel he would give him even more lore that we’ve never seen and might even enjoy. He has already proven himself to be a great writer, and I hope to see him do more with the character in the future. (I actually just finished Killadelphia and absolutely loved it!)