One idea that I think could be wrong is the idea that we will lose many of our traits that no longer become useful, like a sense of humor, sexual attraction, emotion, creativity, art, music, athleticism etc. I think that the principle that whatever we don't need would eventually go away is valid in nature.
However, before that has a chance to take effect, we will likely start to self engineer ourselves and merge ourselves with technology. And what types of things do you think people will aim for when they do that? Probably better sense of humor, attractiveness, creativity, talents in art and music, athleticism, ability to drink lots of brandy. etc. And I think that once that starts happening, people will start going crazy with it, trying to outdo each other. In the end, those human traits we thought would evolve away would end up being hyper exaggerated through genetic engineering and augmentation. The drawbacks will be the neglect for things we didn't think of, and the mistakes we make along the way.
Well, humans happen to have these trait and value them. Humans are also a certain type of creature. We're social creatures, omnivores, and no fangs.
But we have no idea what aliens would be like at the point they start self engineering. Maybe they were carnivores with sharp teeth. Maybe they valued mouths full of teeth, scary looks, and growls. Maybe the more teeth they have the more attractive they are. Maybe they never really needed clothes much before, and don't like them. And maybe these traits hadn't drifted away too much after losing their evolutionary advantages. So now they have
crispr and every alien parent wants their kid to have the scariest mouth full of teeth and the loudest most intimidating growl in town and they're competing with each other. By the time they've become interstellar, their technological and biological augmentation will have made them practically immune to biological threats, air pressure differences, thermal differences, or air composition differences. So then why shouldn't they be scary monster looking creatures who jump out of the spaceship naked and tool-less and go on rampages?