I think millenials/gen z would love to have sympathy for the elderly or others in general, but they are caught up trying to have any future at all in today's world. It seems cruel, but nihilism and dark humor are great coping methods to avoid being overburdened by all the bad things we can do nothing about. Yes, the elderly may die a little sooner than they would've liked after living long and fulfilled lives. But the young people making these jokes are probably struggling with the idea that they may not even live half as long as "those boomers".