"Their bacteria and yours would probably kill you both."

There may be some truth in that. I suspect that even if there are earth-like planets in our local volume of the Galaxy, and that they are inhabited by intelligent beings (by no means impossible),their habitats are likely to be different to ours in significant ways. I'm thinking in terms of radiation burden, atmospheric composition, gravitational field, biochemistry etc.

I've often wondered if we're more 'tied' to this planet than we imagine. Is it possible that humans could never thrive away from the planet Earth or that aliens could never thrive away from their homeworlds?