Yikes, there is something
about those CG shots which put me off, but objectively I can't really fault them.
The only thing thats coming to mind is maybe it looks a little washed out? Some contrast may help? But then the live action shots look very washed out too, so that seems to be look they're going for. I can't believe its simply that though.
Maybe it's hitting uncanny valley? I really don't know. But I'm looking forward to the film.