Is it ableist to want a cure for your severely disabled child?

I read an interesting article today about a line of ethical thinking I had never considered in any depth before.
It was written by the father of a severely handicapped 13-year old who suffers from GRIN Disorder, a rare mutation of the GRIN1 gene that leaves him with the cogition level of a toddler, unable to walk, talk or feed himself, and prone to alarming violent outbursts.
The father and author sounds like a veritable saint, deeply loving and absolutely devoted to his son, despite the almost complete absence of feedback and responsiveness from his charge. He spends most of his waking hours pursuing a cure for his son's affliction, advocating for disability rights, running a podcast series called Unlocking Bryson's Brain for the parents of other GRIN kids, and acting as CEO of CureGRIN, an organization specifically focused on finding a cure for GRIN Disorder.
And it is this obsessiveness with curing his son that now has him reconsidering his motives and his ethical stance, after an anonymous reviewer of his podcast left this review: "I'm sorry, but this guy's not a disability advocate. He's an ableist who is obsessed with transformation".
The "ableist" label - a label I had heard of but not really thought about much before - really stung the boy's father, and this man, who had previously devoted himself to trying to make his son's life "better", and in spite of a whole load of positive feedback for his podcast, has suddenly started to second-guess himself, and wonder whether he has been doing the wrong thing completely all these years.
Ableism is, in general, discrimination against people who are disabled. But this particular ableist taunt came from a disabled person who believes that, if you are disabled, then that is the way you should stay, and that to look for a cure implies that disabled people are less than human and need fixing. There are disabled people who say they would not accept a cure for their conditions even if one were available, even if it meant they could leave their wheelchairs forever. This is an argument I have heard with respect to Down Syndrone and autistic individuals, but I imagine that it is an extreme ot radical viewpoint, and not necessarily representative of the majority, although I don't really know. Nor am I willing to wade into the debate too far.
But it seems to me that this is an argument that is just not applicable to the case in point anyway, because this 13-year old is not cognitively able to make his own decisions on this, or any, matter. So, how can it be so wrong for a doting father to want what he sees as best for his son? Is it so wrong to want to be (or to want your child to be) neurotypical, to want to be "normal"? That he wants, against all the odds, for his son to one day be in a position to make his own decisions on things, to be able to write reviews of podcasts, etc. Because without a cure, this is not just going to happen.
I also feel very sorry that this father, so laudable in most people's eyes, is now in a stressful moral quandary about something he has devoted most of his adult life to.