This isn't an argument for or against the comment or the OP, but this is not universally seen as objective, and there are more ways to think about this than the medical model where there are "normal" people and that disabilities are deviations from what is "normal". Many disabled people and experts on disability see it as socially constructed, because certain conditions (e.g. being shorter than average), while limiting your physical abilities, are not disabilities because society generally provides for those conditions and extends equal access. If 50% of people were born Deaf, our society would still function, but it would address Deafness with affordances like the ones currently offered to short people.
To put it another way, despite e.g. being gay or short posing various social or physical disadvantages, we shy away from encouraging conversion therapy or height extension surgery by default, instead opting for a more inclusive society. And human beings are complex — a person who has found culture and meaning as a member of the Deaf community may disagree with you that they are "objectively worse off" for not having hearing, despite the obstacles.
This article I think does a good job of explaining the quandary of a parent faced with a "fix" for a condition that is challenging but through which people have developed identity and culture. I am lucky to not currently have to take a stand on the right choice here, but I think the complexity of the issue deserves more respect than to be dismissed out of hand.