Sort of. Without random variation we are really limiting our potential, and will be relying heavily on genetic analysis and reproductive control via law to prevent what will become, at least initially, increasingly common recessive diseases.

See purebred dogs.

They absolutely are wrong from a scientific perspective.

Quick sidetrack: There’s a lot of misunderstanding about what people of the time meant by eugenics, because it’s rightly been associated with Nazis. That’s just where eugenics inevitably winds up, and it can’t and shouldn’t be uncoupled from that history. But prior to that it was considered a progressive cause, because the ideal was to reduce or eliminate human suffering by stopping disabled people, criminals, and other people considered undesirable from having children and thus preventing more disabled people, criminals, etc from being born to begin with.

But that’s not how genetics or criminality works. Most disabled people aren’t born with their disabilities, and those that are aren’t necessarily inherited from their parents; with deaf people for example, the vast majority have two hearing parents and they’re deaf due to a de novo mutation. If no deaf person has children ever again you would still have roughly the same number of deaf people in the world.

In addition from a genetics perspective, eliminating a trait from the gene pool can have weird, unexpected effects downstream. Maybe once you remove a lot of these things you think are undesirable at the same time, it causes a collapse of something else you didn’t even know was related.

You can't escape the inter-connectedness of human body systems. Improve something somewhere, something else gets changed too. This is why being a doctor is so hard.

So, it's only true from a 19th century understanding of science. Which a lot of people admittedly prefer, because of how simplistic it was. It's a lot easier to feel like you understand things if you just ignore all the complex and hard parts.

I see the main issue with anything theoretically "sound" is that humans are making the decisions. Human bias, and forgive the drama, make everything worse including science.

Look at what we've done with the environment, introducing invasive species, pet-breeding, colonialism destroying literally tens-of-thousand of years of culture and people because we thought we were "right".

There's an inherent arrogance that's led us into this mess and only recently some have thought to ask "hey, these people and culture have lived and thrived without disrupting the natural ecosystems, let alone cause measurable changes to the climate - maybe they're experts in how to survive and nurture this place?

People will use whatever justification the can readily grab to do incredible destructive things and forgo responsibility by referring to science or religion alike. We can do better.

As for just trying to create healthy humans, we can see that idea failing with crops. We selectively bred the healthiest crops, then everyone wanted that best crop, and now the pests for that crop flourished, meaning they're usually even more sickly than other crops and we have to constantly keep them alive with pesticides.

Eugenics in general has many problems, though. The most fundamental problem is that, whatever one might view as an ideal human, is completely arbitrary.

Even if we ignore obviously existing personal biases, there is no fundamental reason why a muscular man is good, for example. In the next few decades, we might see full automation of manual labor. Then those muscles are irrelevant. And we might see ever hotter temperatures. Then having a bulky body might actively be bad for cooling off.
Or maybe tomorrow, there's a massive volcano eruption, which causes oxygen levels to fall and food scarcity. Then a slender man might be best adapted to that situation.

There's just a million ways in which our situation can change all the time. And the best strategy for dealing with that is diversity.

Which is the second fundamental problem with eugenics, it necessarily reduces diversity.

Diversity is also what prevents singular pests/illnesses from being able to wipe us all.

But ultimately, diversity is also great, because we live in a society. People with different strengths and weaknesses can work together, usually indirectly by just taking up different jobs and paying each other to perform our respective jobs.
In particular, a weakness in one field can also push us to develop greater skills in other areas. Had I been able to become a super model, I wouldn't have pursued an education as fiercely, for example.

The Nazis did that, breeding blonde-haired blue-eyed people (mostly combining German men with I think Swedish women). Most of them were murdered after the war ended (despite only being innocent children), because people thought that 1. Nazis have to be mentally different and 2. same for women who "agree" to participate in this program, so they thought that of course the offsprings would "also" be mentally different/disabled.