Yes, this will lose some new beneficial mutations, but since most mutations are deleterious, taking majority allele is guaranteed to be an improvement in whole. Huge improvement.
Duplicate some hollywood star's genes ? Maybe even a scientist's ? Some combination ? Perhaps (have fun being the first one to try it though). "Perfect" genes/humans ? No way. It'll take decades before we can create smarter humans. "Duplicate" your beloved pet ? Sure (domesticated animals are pretty close to clones already, but whatever).
However, it'd be much easier to create the perfect dishwasher/street wiper/soldier. Obedient, maybe even dependent on a drug and unable to reproduce by themselves (ala Monsanto plants). And the question isn't whether we can stop the US military from doing that. The question is whether we can stop China.
I.e. get the "secret" formula for a unique hair color or body proportions, or whatever.
If everybody's "perfect" in the same way, there's no advantage to being perfect, and people will look for ways to differentiate.
(Of course all of this is Hollywood-level speculation, but still).
The most obvious being, what exactly is perfection? If you ask 100 people to describe their perfect partner, you'd get 100 completely different answers. If our species would converge to any one of those descriptions, those who have a different idea of perfection would find themselves in a objectively worse world. Converging to some kind of average wouldn't be any better either.
Just take a look at the standards of beauty even over the last, say, 40 years. There's no constant, purely objective measurement of beauty, so to me it seems impossible to create perfection.