I completely hear your point. We have a close neighbour with a kid with a mental disability which causes her to mentally stay forever 6 years old. She is a happy person but we do see the effects on the parents and sibling and how much care and love they spend. They do it willingly and lovingly, but it still takes a toll. Would they choose differently? I don’t know. But as a parent if I had the chance up front to cure/fix/prevent expression of Down syndrome, I would take it.