That's not feasible. Those people have families, too.
They can't even realistically do this with the NBA and associated support staff, and that's a hell of a lot fewer people than vulnerable/old people and their support staff.
I, too, wish it were that easy, but it's simply not.
Why not? I don't think the parent meant staff should stay on-site forever.
There can be shifts. Staff on shift get tested or even stay isolated for two weeks, then enter the unit, spend a month on-site and leave for home.
Does this sound like a dream job? Not really, I guess.
Does it sound that different from sailors, long-haul drivers, deployed military personnel and many other professionals who stay away from their families for prolonged period of times?
It has to happen, because people cannot stay inside forever, with all the will in the world.
This is definitional unless you're planning to create a police state and forcibly prevent the young from interacting with each other for years at a time.
Protecting the vulnerable is the only practical solution.
It is not a practical solution because there is no political will to do it and there is not the competency to do it even if the political will was present.
So we have four weeks of quarantine for every month worked. That means we would need double the staff, and also we would have to pay them way more to even find someone willing/able [1] to accept this shift arrangement. This means that a huge part of the inhabitants will be priced out of the nursing home market and forced to stay at home with inadequate care.
[1] Re "able to accept this", for instance, single mothers would not be able to work under these conditions at all.