"Progress" is something that emerges only in hindsight, and is a value judgement that embeds a perspective from which it is made. What we have in the present are choices, and possibilities, and estimations of their outcomes.

You could oppose this because you think it's unlikely to work at all, and so is a dead end and wasted effort. You could oppose it because you think it will work, but that the changes are not likely to be improvements.

Is a procedure that creates a new form of smarter, healthier, longer lived human progress? For them it certainly is. If they deny me that technology for my descendants, is it progress for them?

It is simply not going to break down so easily into "this is progress and progress is good." It will have consequences, some of them negative, many of them unexpected. It will be better for some people some of the time and worse for some people some of the time, like almost all changes are. Resisting change simply to slow it down and better understand and predict the effects is a valid stance as well. None of these things are inherently unethical.

Would you volunteer your child for experimental gene therapy to make them HIV resistant, a therapy that has never been proven to work and has an unknown risk of permanent side effects?

Imagine laws that sanction mandatory "improvements" on the future subjects. To me, in that context, this "it's grossly unethical to stand in the way if that progress" is where the true (as in hardcore) politics begins. (Compare to that, the current politics, which deals in easy amendable decisions, feels like child play.) Then there is this dynamic we can all see in software development, with haste of feature addition and not much regard for other lesser aspects (in the marketable sense), that may cross into gene development. There are many more interesting angles that will pop up if you give it a thought...