But embryos are people too.

Eh, they’re not people yet.

How many potential sibs can you waste for the perfect child?

Human bodies produce way more gametes than most people want children, so I’d say that one could “waste” quite a few.

Not everyone can benefit from gene therapy, so it is not truly a benefit to society or humanity, and therefore should not be developed

Strongly disagree. While socioeconomic inequality is an important issue to address, that is no reason to halt scientific research and technological progress.