While this would certainly be a blow for science in general, I don't understand why people are so enamoured with human space travel and think it's a realistic avenue for humanity to get out of the responsibility we have for Earth (there's the strange defeatist sentiment on the internet that we have to leave this planet in the foreseeable future).

Fact is, the laws of physics probably dictate that we won't ever leave the solar system and in our solar system there's not much we can work with to make the other planets habitable. It's comparatively soooo much easier to simply make life sustainable on Earth and then figure out space travel in the thousands/millions of years we have left until some external disaster (asteroid, exploding sun, whatever) threatens us. In the meantime, we can explore space efficiently with robots.