All very fair criticisms. I won't lie, I'm not a huge Hickman fan so I've only read a few things of his, but what I've read I've enjoyed overall. I do feel he can focus on the characters and not just his world-building when it comes down to it, but I will agree that his complex narratives/worlds do tend to come first from what I've seen. I wasn't a huge fan of Full Circle in general but I really loved the absurd humor especially in Hickman's story, but I recognize that's just a thing of taste. I think you make plenty of good reasons that Hickman may not be a good fit as well.
Edit: Maybe pair him with another writer who handles the actual scripts/dialogue? Have him be a big ideas guy while someone else makes those ideas realistic in a fun comic script format.