Slippery slope arguments are inherently flawed. We’ll keep this within the frame of the discussion as presented.
If money was no object, and everyone had the SAME access to the technology and equal medical providers, etc, etc.
Would it be unethical to choose what attributes your child had from the gene pool of his or her father and mother (and no one elses), repair any genetic mutations, cure any genetic diseases and repair any birth defects?
Or, another way to think of it is:
Is it more ethical to allow nature to produce children with brain damage, who are born addicted to drugs and/or are born with serious physical handicaps just so that you can say that medical science had nothing to do with it? Or is it more ethical to allow medical science to fix these problems at a very early stage, but allow them to also give the child his Mother’s eyes and his father’s chin?