They're missing a big piece, though. Including diverse characters can be political but does not have to be political. There is something to be said for the all-black story, the all-women story, the utopias and dystopias in all their manifold variety, the story about a boy and his disability. The more overt the featured motif, the more political the story tends to become. And the harder it becomes to do well, because people disliked being preached at.
Some of the best stories, however, aren't political at all. How to Train Your Dragon has disability right at the core of it, but it's not about being disabled. Yet it shows us that losing a tailfin doesn't mean you can't fly, and losing a foot doesn't mean you can't train dragons, as long as you've got some good equipment to make up the lack. The message is there, but it doesn't beat you over the head. It's an adventure story -- and also an interspecies platonic love story -- not a manifesto.
I write political stories sometimes. My parents, both teachers, often give me explicitly political prompts which I may write straight or slant through other worlds. A lot of what I write, though, is just that way because it's what I see in the world. There are men, women, and assorted other sexes; I put them all in stories. I use different races. I love lots of languages. There's a photoshoot of Olympic athletes for diversity in heroic body shape. I have literally written things, repeatedly, that I didn't even realize I was putting in there because I was just writing what I observed -- and then years later, I'd find a reference describing the thing, and oh! yeah, I wrote that 20 years ago.
If you want to slap people in the face with "We're here! We're queer! Get used to it!" then by all means do so. Some people need a wake-up fish across the face. But it was Kirk/Spock that drove the rise of slashfic, and that is a big reason why the unspeakable became the adorable. Not with a brick in the air, although gods know we needed Stonewall too, but with mimeographed beach reading that nobody thought was important ... except that you kinda can't read IDIC without getting some on yourself. Over time, it really soaked in.
When you're writing inclusivity, then, think about whether you want to be political or not, dramatic or subtle. They both work. But they work in very different ways, and you should think about what response you hope for before you decide which tool to use.