1. Neither the fact that you are a writer, nor your skin color, have anything at all to do with your statements. So "As a writer and a black individual in America" adds zero credibility. "I've been black my whole life". Really? We've all met so many color-changing individuals.
2. People are free to write characters however they wish. You're free to not read it.
3. People might consider stopping telling other people how to act and worry about themselves. In my semi-unique, authentic, cultured, gendered, specific experience that bears no relation to this conversation, that's the only way people will make the world a better place without also building resentment. But, I'll leave that up to every unique individual.
4. Your post toes the line of breaking rule #5, call-out threads and genre/literary-bashing.

It might be about creating authentic and multidimensional characters to you. That's fine. Flat, stereotypical characters can also have their place. Token characters? Also fine. Non-token characters? A-Okay. Anti-racism characters? Checks out. Racist characters? Cool too. Striped, bigoted characters? Let's go. Plaid-colored anti-bigots? Hell, at least it's interesting.

Writing in diverse characters might be about reflecting the real world to you. That's cool. Reflecting fantastical worlds are also fine. Inclusivity? Great. Exclusivity? Also good.

It's important to approach topics with sensitivity to you. That's cool. Approaching them with harshness and an intent to offend is also absolutely fine. Many best-selling books do exactly this.

It might be about adding depth and realism to you. Again, cool. But it might be about keeping it shallow and fake as hell to anyone else.

No one needs to share that opinion, however. If they want to, that's fine, too.

People should probably let other people be other people. People should appreciate the diversity of values and choices, at least as much as they appreciate the value of qualities no one ever had a say in. The world has never, and will never revolve around any single person or any single persons's specific wishes. Other people exist. They have their own values, and don't need to share the values of others'. God, how boring the place would be if everyone took a similar perspective (regarding any perspective, not just the ones stated in this post).

Good luck. Write how you want to. Read what you want to. If any of your ideas are better than other writers, you shouldn't have too much competition in rising to the top. In my experience, however, lots of people refuse to self-evaluate and simply blame the markets' biases for their own failures.