I hope I live to see the day when we humans can die on our own terms rather than it being forced upon us.
In an alternate Earth where humans never aged to begin with and society started stagnating (or worse) because of it, I doubt that the world's top minds would come up with 'kill literally everyone at X years of age' as their first option (or second, or third...). That would be comic book supervillainy.
These kinds of concerns aren't invalid, I just hope they are considered with a wide enough perspective. In terms of direct and indirect suffering, it's hard to do worse than aging.
Needing societal innovation does not mean you're going to get societal innovation, though.
Also, a cure for aging does not mean that nobody will die from old age. It means that the people who can afford the treatment won't die of old age. The poor will continue to die.
But they are not unsolvable problems, nor do they imply that aging is better than agelessness. They just imply we have to work harder, because again, the alternative is the death of everyone.
Without death by aging, this moderating influence wouldn’t be there, so we’d see far more assassination attempts and coup staging.
Also "stagnating the status quo for centuries " sounds bad because you expect to live decades. If you say it as "stagnating the status quo for time comparable to half of the human lifetime" you'll see it's not any worse than what we have now.
I am going to live and die on my own terms, unless it is a sudden unnatural death (ex. Accident).