Truth be told, the authors who get big in ownvoices spheres are mostly the ones who've cultivated it as their brand. They set themselves up as Authorities On Diversity, and it serves a twofold purpose of letting them attack rivals on specious grounds of "diversity" (look, this person's book is Hurting The Children! Get them!) and shielding them from any criticism themselves, because of course The Authority On Diversity couldn't mess up in their own books! Look at authors like Mark Oshiro, whose misogyny goes unchallenged because he makes such a big deal about other authors' perceived racism/homophobia, or Justina Ireland whose online bullying meant her treatment of Native American characters in her books was treated much more gently than anyone else's would. It's nice work, if you can get it.