CoolSchool, I see your point, and the euphemism treadmill can get tiresome when certain conditions are perceived in a way that means any new term chosen is eventually repurposed as an insult.
But that process doesn't seem to inevitably happen with all conditions with some terminology that has become pejorative. Maybe there were some small groups that briefly used the name of the Scope charity to substitute for an insult they were no longer allowed to use, but I've never heard it used, and I've not heard cerebral palsy, palsy, CP etc. used like the insult derived from "spastic" was, either (am reluctant to type it because a while back I had a post automatically insta-deleted because I was discussing various disability slurs).
The medical community can't keep inventing terms that people feel more comfortable with when everyone knows what they mean
But they've done so with many of the terms you list in your later post. Thankfully, I've never had to see a parent posting on MN who's upset because the computer screen at their child's GP appointment said "Moron". And spastic is still used as a medical descriptor of what a body part might be doing, but cretinism has gone (the name and to a large extent the disease, in developed countries at least — but even with fewer people affected, they still went to the trouble of changing the name to "congenital iodine deficiency syndrome").
And now "hypochondria" seems to be gradually disappearing from medical communications with patients and the public, too, in favour of "health anxiety" or "illness anxiety disorder".
It's not much different to "idiot" in some ways. Like "idiot", it's an obscure Ancient Greek term, which even if you understand Ancient Greek, bears little resemblance in meaning to our modern understanding of the problem it's used for. So, unlike "illness anxiety disorder/health anxiety", or "profound learning/intellectual disability", it gives people no useful info besides being a unique verbal identifier for the disorder. And on top of that, it's commonly perceived and used primarily as an insult. There are big differences too, but lots of parallels.
So besides medical inertia, what's the benefit of clinging on to an opaque, misleading Greek term that doesn't help patients understand or communicate their problem, that might upset or offend them, and that they might be reluctant to communicate to others?