The problem is that most sheltered housing schemes (McCarthy Stone etc) don't provide "a substitute for the care, supervision, interaction, company etc that a used to be provided by family."
What they do provide is physical accommodation which is better adapted to the needs of older, less mobile residents - small, manageable, no stairs, accessible bathrooms and so on - with some kind of residents' lounge for a bit of optional community activity, and sometimes limited catering facilities, plus a manager who may be there for a certain number of hours a day. There may be an emergency alarm button scheme in case of falls or emergencies. This is all great for a person perhaps in their 70s or 80s, still independently mobile but finding the old family home too much to cope with.
But once a resident reaches the stage of needing regular care, that is still usually up to the individuals and their families to provide or arrange, and many schemes have rules which say that residents with high care needs, eg those in advancing stages of dementia, cannot remain in the facility.
If you want to guarantee care, supervision, interaction etc, then you are looking at a care home, not a retirement property.
I would only ever advise renting a flat in a retirement development, not buying one, because the chances are high that an elderly person will eventually need more care than can be provided there (I speak from experience).