
I'm going to paraphrase something someone else in the forums said once: Remember that Player Characters are a subset of remarkable characters, who are a subset of all perceivable characters in the world, who are in turn a subset of all people living in Eorzea.
So while it might be true that most of the old people in Eorzea aren't combat capable, it doesn't need to hold true to most of the Player Characters. Unless a player decides to purposedly play an unremarkable character (it happens), there's no lore reason to not have an old badass. In fact, there are plenty of lore reasons to do so: namely, aether. Except for those who have low aether naturally, everyone is able to use magic to some extent. That's why every class and job has a special and flashy effects, and that's the only way you can justify someone being able to punch Titan in the knees and cause damage. If everyone can use aether to enhance their capabilites beyond the norm, then it is very likely that the aged people of Eorzea would be able of many feats as long as they had the training during their youth or as long as they keep fit.
For example, the leader of the Ala Mhigan refugees in Little Ala Mhigo is an old grizzled man. He wears an axe and he accompanies you in one particular quest to fight some enemies. He is not tired, winded nor wounded afterwards.
What is true is that they probably will not be as effective as someone with the same ammount of experience who is also younger. But that's getting into technical disadvantages: the oldies can fight too, and the game supports that idea.
So while it might be true that most of the old people in Eorzea aren't combat capable, it doesn't need to hold true to most of the Player Characters. Unless a player decides to purposedly play an unremarkable character (it happens), there's no lore reason to not have an old badass. In fact, there are plenty of lore reasons to do so: namely, aether. Except for those who have low aether naturally, everyone is able to use magic to some extent. That's why every class and job has a special and flashy effects, and that's the only way you can justify someone being able to punch Titan in the knees and cause damage. If everyone can use aether to enhance their capabilites beyond the norm, then it is very likely that the aged people of Eorzea would be able of many feats as long as they had the training during their youth or as long as they keep fit.
For example, the leader of the Ala Mhigan refugees in Little Ala Mhigo is an old grizzled man. He wears an axe and he accompanies you in one particular quest to fight some enemies. He is not tired, winded nor wounded afterwards.
What is true is that they probably will not be as effective as someone with the same ammount of experience who is also younger. But that's getting into technical disadvantages: the oldies can fight too, and the game supports that idea.