Agelessness might cause some social problems, but if the choice is between "everyone dying" and "needing societal innovation to avoid stagnation", it's hardly a choice at all.

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.