It appears to be possible from what you've said about your grandmother's situation that even if her inheritance was not taxed at all she would have still ended up using up all of her savings on care. If your point wasn't that you believed she should have been able to pass along the millions to her children while receiving care at the expense of society then I don't see how it was relevant.
I just thought the downvotes were uncalled for. And I think your threshold for what's a reasonable estate is both arbitrary and too low.
$5 million sounds like a lot, but give it a decade. Many family businesses are already valued over $5 million. Should functioning businesses be liquidated because the founder died? Soon, family homes in places like NYC, SF, and DC will be within spitting distance of $5 million. Should the family have to get a new mortgage or move because grandma died?
Besides, I don't have confidence that the general fund of the federal government would better spend that money than someone seeking health and indirectly pouring money into better medical science and technology.
If the government took most of that money, this grandmother would have burnt through the remaining money quickly and ended up on government-assisted healthcare with much less choice about the kinds and quality of care. It's very pertinent.