I find the claim that people think of the old, or those with health vulnerabilities, as "expendable" really odd.
It's that word specifically, as if anyone is saying "oh well, we can get along without them, no great loss".
It's really not about that, in fact I would say that I think each person is deeply precious and worthwhile. But at the same time, it's a matter of understanding that we are all going to be expended, we are all going to die. Whether we like it or not, it is completely unpreventable, and if we think somehow we can prevent death, we are living in a foolish dream.
And what causes people to die - well, diseases, degeneration of the body by age, accidents that leave us damages. All the things that make us vulnerable. That's what being in a vulnerable category actually means - your chance of dying is higher than that of someone who does no have that vulnerability.
Typically as we age we start seeing people in our peer group die as we get into our 50s/. Maybe only one or two, someone succumbs to an illness they had in youth, they have a heart attack, cancer. A few more in your 60, and then into the 70s you get a bit more and so on. Some will remain healthy and active, through much of that time, but by the time someone is in their late 90s most of their peers will be gone. Because as we age, more and more vulnerabilities come to the fore.
If the idea with covid or anything else is to somehow create a situation where the vulnerable aren't in fact more vulnerable than anyone else - how exactly does that work? Saying we recognise that they are more at risk, that more will die, that we can expect that, does not mean we think they are expendable. It's just a recognition that everyone dies and the more vulnerable are likely to do so sooner.