Ok, so for context this is coming from someone who has studied race and gender and I teach ethnic and gender studies in my college courses, so buckle in...
I totally get where you guys are coming from, but I think you may be missing a key component to what this movement MIGHT be trying to accomplish: representation.
I don't believe the "Own Voices" movement is about preventing stories of diversity, but rather, it is serving as an opportunity to give under represented groups a chance to tell their stories from their perspective. This movement is happening because for sooooooo long, the conversation in the arts has been absolutely dominated by white, heteronormative, straight, men. That is the prevailing voice, and when THAT voice tells the story of someone of color, someone who is oppressed or marginalized, it is a form of cultural/soci-economic/gender/etc. appropriation. It is a form of intellectual tourism. If the conversation as been only focused on one group for so long, I think publishers are now trying to create more opportunities for other points of view, or frames of reference. I personally believe that the industry is looking to find new and upcoming artists and authors of diverse backgrounds to tell diverse stories. This helps them avoid looking as if they are simply placating or pandering to a more diverse population by presenting stories of diversity from authors and illustrators who are not, in fact, "other".
I don't think it means you cannot include a diverse cast of characters. I dont think it means as a white illustrator I cannot draw black people. What it DOES mean, is that I should exercise caution before telling the story of a child of color growing up in abject poverty because that is a life experience I cannot adeptly speak to with authenticity.
A couple of things here: Please be careful of falling into the 'we are all humans' or 'I don't see color' trap. I know when people say that, they mean well, but what that does is erase the diversity of many marginalized groups who have been made to feel sub-human for centuries. What many oppressed groups want instead is for you to see and recognize, and RESPECT their differences, not erase them when they make you uncomfortable.
Another comment that I think needs to be addressed is @mattramsey's comment about the intersectional unicorn. I get where you are coming from. Psychologically, there are things that ALL humans feel. Getting punched hurts. Having your heart broken sucks. Making a new friends is awesome. But THOSE is not the type of stories I believe the "Own Voices" movement is trying to tell. Of course anyone creative can imagine what it may have felt like to be picked on for being gay, or fat, or black, or disabled. But if you are none of those things, you don't have an honest place from which to tell that story. You may accidentally get some of it right, but wouldn't an authentic voice from someone who has not had the same opportunities to share that story be more powerful? Wouldn't that be an opportunity to learn and grow? And perhaps more importantly for the AUDIENCE (who has been alarmingly missing from this discourse) wouldn't be awesome to see yourself represented by someone who is like you? THAT is what this idea is really supposed to be about. Representation
Also, I hope before you spout off about "gay, asian muslim men" or "transgender lesbian black disabled women" as some sort of "holy grail" of diversity you stop to remember that those labels ARE attributed to and DO affect REAL people. Some people don't have the privilege to only wear those labels to write or illustrate a story. Some people have to live it every second of every day...and every action they preform or interaction they have is colored by those labels. Understanding privilege is a great way to help see the other side of the story. I can PROMISE you without a doubt that anyone identifying as any combination of those labels you tossed so carelessly have been hurt by, or discriminated against in ways you take for granted every day. The transgender lesbian disabled black women has to worry about that building having wheelchair access. She has to worry about getting jumped for using the "wrong" bathroom and she has to hope the store manager doesn't follow her around because she looks like she might steal something. She has to worry about getting mugged because of who she loves. Because of who she IS. That is her life. I can assure you she doesn't see herself as some coveted intersectional Holy Grail.
What the "Own Voices" movement realizes, that many people here seem to be missing is that you simply CAN'T know all the myriad and nuanced ways the daily life of those different than you are impacted by being different. You can try to, or pretend to, but that is just it. It's not real or authentic. Maybe this topic is not as relevant in children's media but it certainly is a big issue in almost all other forms of creative expression.
One final thought on why diversity in children's media is so important, and why having authentic voices share those stories is so valuable: Steven Universe. This show is an excellent example of diverse characters who are not telling stories ABOUT diversity. They are written honestly and authentically without losing the target audience. And the creator speaks very eloquently about the importance of LGBTQ representation for young children. Hope this helped provide some context.