This is a fair question. And I've had philosophical problems taking psychiatric drugs, for that matter. (I think it's resolved to some extent by considering that lots of substances we ingest all the time are psychoactive. So it's part of the normal human experience.)
I would say this - Whatever modification you make, you have to come up with a line, a standard, for which you argue "this is still a human." I draw that line at deliberate engineering of genetics. What is yours? Are there some genes that still shouldn't be edited? Maybe you could draw some line there?
OR, if you think that's a silly question and don't care about what is or isn't a human, let's revisit the equally silly assumption that we should care about propagating the human race. I personally feel like if you take such a nihilistic approach to the definition of human, you may as well go all the way and adopt an anti-natalist position. It's just not clear any more what game we're playing.
> All the scientists condemning this as terrible, and articles written about the dystopian future it portends.
Interesting, I'd expect scientists to be on the pro-side of this. I don't know have a strong opinion on the consequential outcomes.
(Made some edits above)
I also don't see how this relates to the instinct to procreate. We don't procreate because we think its the "human" thing to do, we do it because we're human and we have an instinct to procreate. If procreation conflicted with some other drive or interest of ours, we might decide to forgo it (and many do). But this doesn't seem out of bounds of what is typically human either.
I think the burden of proof is on the person asserting that to say why it is so. We alter ourselves in lots of ways, why is this different?
> EDIT: What hysteria were you talking about?
All the scientists condemning this as terrible, and articles written about the dystopian future it portends.