Most people really don't seem to know what this mysterious "residential care" means when it comes to disabilities.
"This person is severely disabled, they have to live in residential care."
Do you know what happens when a severely disabled person with high support needs who isn't aware of dangers and needs constant supervision applies for residential care?
They get turned down or kicked out a couple of days later.
This happens regularly, btw. Kids grow up and parents think "Oh, residential care sounds good", and then suddenly every institution, etc. goes "Sorry, we don't specialise in that, sorry, your child is too aggressive, sorry, your child can't stick to our sleep schedule, sorry, your child is too noise sensitive, sorry, your child HAS to participate in our weekly activities even though their disability makes it impossible for them to do so, sorry..."
People who can live in residential care aren't your "the worst of the worst" example. There is such a thing as "too disabled for residential care" and it's more common than you'd think! ☝🏼
"But what happens when someone is too disabled for residential care and their family can't take care of them? Surely everyone eventually ends up somewhere!"
They get passed around from institution to institution, but everyone eventually goes "Sorry, we can't keep them here", and it won't stop. Until, maybe, one day they're lucky and a fixed team of carers "adopts" them and tries to create some kind of assisted living from scratch.
Nobody talks about it, which is why it's always a big shock for parents who found a really good residential care place for their soon-to-be adult child and their child looks forward to moving out, and suddenly this wonderful residential care company turns their child down because it's too disabled. And then the next one. And the next.
So no, residential care isn't for "those with the most profound disabilities" - people with the most profound disabilities can't be in residential care at all.