I one person who isn't sure about that. I don't see why it wouldn't be good for us to evolve into something more advanced. Whether that's through melding with AI or advanced genetic engineering that outcome could be fantastic (assuming the transition is well managed, broadly distributed and happens through choice etc). It could lead to elimination of disease, aging, reduced ecological footprint, all kinds of benefits. And of course we've evolved before, it would be sad I think if this was the final state - I think we can do better!
Pretty sure AJ007 wasn't including transhumanism in the things they were calling "human species extinction", so I doubt you actually disagree.
I don't think people are primarily concerned about this outcome. They are more concerned about outcomes like "all the matter and energy in our light cone have been repurposed to maximize the total number of paperclips".
On the plus side it eliminates all human suffering. So from a negative utilitarian view it's a win. Unless, of course, there are more-suffering species out there that humans could eliminate suffering for.