Also, this is more of a technological question, but how are these signals transmitted? From my rudimentary understanding of physics and space, there shouldn't be any theoretical limit that a radio or similar signal could travel, right? But isn't there a practical limit formed by objects and gravity wells through which a signal could not pass, ultimately resulting in large shadows that our signal wouldn't be able to reach?

Thus, aren't any of the odds of contact hopelessly optimistic because, while we have infinite possibilities in terms of planets on which life has developed, isn't there a pretty small physical limit of locations that we can contact?