I agree with the top answer that dogs are a perfect example of long term eugenically selective breeding, without them dying out (though you could argue that the average small dog is less equipped to survive in the wild now).
However, it seems you're conflating a few things.
mutations in the population would become virtually non-existent
Mutations are an exception to genetics. In most cases, picking a certain set of genes from either parent will give you a guaranteed outcome. Dominant and recessive genes are a basic example here.
Mutations, however, change the expeted outcome. They are unforeseen and happen randomly. Mutations will occur regardless of whether you handpicked the genes (eugenics) or shufffled them randomly (biological reproduction).
The only way to prevent mutations from occurring would be to alter the biology of actual "baby generation" (I can't find a better name for it). Most eugenics I've heard of (including fictional) generally revolves around picking the desired genes but still letting nature take care of the actual "baby generation" process.
because they almost always are initially a disadvantage (until adverse environments are formed)
Adverse environments are not formed because of existing mutations. Mutations do not occur because of adverse environments. These two things are separate and coincidental.
A mutation which coincidentally happens to solve a problem, will enable the mutated animal to have a better chance at surviving an adverse environment, thus allowing the animal to reproduce more and generally spread its mutated genes around.
Disclaimer: My answer focuses on practicality, not ethics. I'm not personally advocating eugenics.
My first question is whether I am over-exaggerating the issue?
Referring back to what I said before; I think so. Mutations will still occur. There are three possible outcomes:
- Positive mutations have a habit of sticking around. This applies to nature (more reproduction, either through increased survivability or mate selection) and eugenics (more people choosing the mutated gene)
- Neutral mutations will generally mean that there's no discernible drawback or benefit, which means it slips by unnoticed (e.g. the color of your stomach lining - no one cares). The odds of the mutation persisting is effectively random chance.
- Negative mutations have a habit of being weeded out. This applies to nature (less reproduction, either through decreased survivability or mate selection) and eugenics (choosing to avoid the mutated gene).
Putting ethical issues aside, eugenics are really just speeding up natural selection. Arguably, being free to choose your mate is selective eugenics. Which means that pretty much every animal engages in eugenics. By selecting the right mate, they are somehow able to maximize the (still somewhat randomized) genetic outcome of their offspring.
Natural selection is a slow, brute-forced process, but it usually ends up consistently improving a species.
Eugenic selection can be incredibly fast and can bypass the brute-forcing stage because intelligent decisions can be made. However, this does open the door to making intellectual mistakes that negatively impact a species.
Two examples of this, one fictional and one real:
- Jurassic World. An dinosaur is eugenically bred to be the most amazing killer, to amaze visitors. And then it outwits the zoo keepers and escapes.
- Killer bees. Created during research. Not intended to be let out of the lab. Then they escaped.
Second, if not, what can the society do to manage the growing trend to survive in such a potential future?
I'm not sure what you're asking here. Regardless of whether a baby's genes are hand-picked (artificial) or randomly shuffled (biological), the baby counts as one life.
Are you assuming that eugenics will increase the amount of babies that everyone has? That eugenics will nefariously implement a "planned obsolescence" in cheap eugenic options?
These are interesting things to explore, but your question as asked doesn't really explore this. What do you mean by
the growing trend to survive in such a potential future?
If anything, you'd expect gene choices (for eugenics) to be made specifically to improve on the otherwise randomized gene selection. If eugenically created babies were somehow more defective than their biological counterparts, there'd be no reason to chose eugenics over the natural way.