Designer babies is the start. Like I already believe if you're "selecting" something like your baby's gender, you're fuckin Hitler. But then, my roommate was all, "Well what if you could remove the trait for Huntington's that runs in the family?"
So there's clearly a spectrum of ways that genetic engineering could go.
The most interesting case to me is of He Jianku, who reportedly began studying and modifying human embryos. CIA fear disinfo, or Chinese scientists just marching ahead and setting the new standards of the 21st century?
I don't trust humanity with that kind of power. Suppose you could travel back in time and give people that ability - is there any point in time when it wouldn't be horribly misused? If not, then don't you think people a hundred years in the future would be horrified at us having it?
Beyond that, like, pain is bad, right? But not having pain would be worse, because pain serves an important function in alerting us to danger. There are all sorts of cases where what we think we want is different from what we actually want, or what would be best for us. Your goals when designing a game are fundamentally different than your goals when playing the game. Imagine you're playing Monopoly and you think, "The object of the game is to avoid bankruptcy, so let's add a house rule where the first three times you go bankrupt you get a loan from the bank to stay in." Obviously this would make the game even more drawn out and tedious than it already is, and is a terrible rule. We can see what a bad idea it is because we are capable of stepping away from our assigned motivations as players. But when it comes to the game of
LifeExistence, it becomes difficult if not impossible to set aside the goals that evolution has instilled in us. Are we sure, for example, that extending our lifespans is something that would actually improve the human experience, or are we doing it simply because evolution has instilled in us a fear of death? I don't mean to limit this criticism to that specific example. This idea of "what you think you want isn't always what you actually want, or what's best for you" is something you can observe everywhere. Like, relationships, anyone?All of that is assuming that everyone using it is acting in good faith with a similar value system to yours. If you had to choose between risking a genetic disease, vs risking being born to some QAnon whackjob who altered your genetic code to their specifications, which would you prefer? Or would you leave it in the hands of the US government, because, you know, what could go wrong? You might say, "Oh but it would only be for such and such diseases we all can agree are bad." All right, well how about we table that discussion until you're God Emperor of Humanity because until then you're not the one who's gonna be making that call, are you? Once you throw in profit motives and brainworms all bets are off.
I recommend Eugenics and Other Evils by G. K. Chesterton for further reading. He was a bit of a tradcath weirdo but occasionally cool and imo he was really on point with this, especially considering he was writing at a time when eugenics was all the rage.