That's not how herd immunity works... there is zero immunity. Caregivers cannot risk infection because their risk to their cared is too great and getting everyone infected isn't a strategy for anything other than mass death.
At that point it will be much safer for the vulnerable
There isn't mass death because the elderly will be isolated, a lot of elderly at risk here don't need caregivers and for the ones that do basic protocols can be adopted
The best hope that virus mutates to a milder form. But that requires the longest chain of transmission so the evolutionally pressure has chance to work. Increasing social distance is precisely what pushes the virus in that direction.
Herd immunity applies to the fact that a certain percentage (usually > 90%) is vaccinated against a specific virus.
You can't herd immunize a population by letting them get sick. What the Brits are attempting, in my opinion, is sheer madness and totally irresponsible. Even when they try to backtrack from the term "herd immunity" now.
Or, how do you think herd immunity ever worked on smallpox, or polio?
Hint: It started to work, when people got vaccinated against smallpox and polio. Before that they got sick in a very misearble way and died. It's not that they ever developed "herd immunity" on a natural way.
I also think that your suggestion to just bunker away old people in your original comment is outright offensive.
I'm buying several months of dry goods tomorrow that won't be touched for several weeks, quarantining myself outside of my mom's home for two weeks, and will stick it out 3-6 months or however long it takes.
But how many elderly people do you think have such support?