Plenty of people vote how their parents did; that's just how values work.
Plenty of people vote against how their parents did; that's just how having your own identity works.
Plenty of people vote who think critically about nothing despite their so-vaunted capacity to; those people are idiots, but we don't require them not to be. And really, most of our politicians could use some lessons in empathy, technically capable or not.
None is a reason for denying suffrage.
And nobody should have to struggle to survive; that's a failure of modern society. And again, it's not something we require old people to be tested for; silver spoon trust fund kids who will never know what "struggle" means aren't kept from voting.
We don't require old people to justify their votes. They don't have to be rational enough, empathetic enough, or anything else enough. Old people can vote by rolling dice and nobody will stop them.