Also, if you actually look at the Trek stories about the genetic engineering ban, they're usually not wholeheartedly endorsing the ban, but rather are exposing its unfairness. (I'm leaving out "Unnatural Selection," which was written before the ban was retconned into existence by DS9.) "Doctor Bashir, I Presume" makes it clear that Bashir's genetic engineering had a positive result, that he didn't turn out evil or dangerous. The later "Jack Pack" episodes do portray some people whose engineering turned out badly, but that's largely because they were engineered illegally without proper oversight or safeguards; and they were still presented as worthwhile people who were just misunderstood and given a raw deal, rather than horrifying mutant monsters or something. And ENT's Augment arc had Arik Soong state explicitly that the reason Khan's Augments were so dangerous was because their engineering was flawed and gave them too much aggression and too little empathy. It wasn't an inevitable consequence of any genetic engineering, but a mistake in humanity's earliest, crudest efforts, one that could be overcome by continued research and practice. The same arc established that Denobulans used genetic engineering without any "devastating damage" or "horrific consequences."