Thor finds botht ideas disconcerting. First, the idea that there are other pocket universes like these that people are sporadically trapped in; second, the idea he might not be able to return home and take care of Thanos himself. Perhaps he should be content to stay here where people were alive and well, but that wasn't an option. Not for Thor.

"Must have been nice to have more to do at least," he says, instead of remarking on Rocket's less-than-optimistic viewpoint.