Having followed qntm's work since Fine Structure (2006), he's really improved since then. He got a lot better at character writing with Ra (2011).

I think it's largely a matter of intentional practice. I think that some sci-fi writers don't prioritize honing that skill, since they just want to build a cool world and the story is a way to demonstrate that.

I have never heard of that book, but a quick Google search reveals that the author is in the process of "releasing version 2". Refer to the previous comment for my opinion on that matter.