I agree with everything you said. My characters are predominantly white. Not because I don't want a black character, but because they "fit" into my story line. I'm currently working on a story with a black main character.
I have a character who is wealthy and I write stories about adults (meanwhile I'm a teenager myself).
The thing is, there's a reason why half the ppl who have replied to this forum doesn't know most of these authors you mentioned. And it isn't their talent. Some authors go for what's popular, others only know how to write what's popular.