AIs can't speak human languages.

No, playing Mad Libs to get new text out of old is not speaking human languages.

We don't even have AIs that you can explain a simple story to and then ask questions of.

Automatic translation requires huge corpora of already translated text.

And there has been almost no progress in strong AI in the last 50 years. We don't have a theory or even a roadmap as to how to progress. Do note that we knew how to get to the moon for a thousand years before we got there.

My best guess from watching humans is that technological creatures inevitably destroy themselves long before they would be capable of interplanetary travel,

None of this will happen.