There’s many ways of defining archetypes but the « what they do » is the easiest tool to use for a rpg.
Otherwise, I remember a few systems running around « how they do it », giving archetypes such as « the strong dude », « the quick guy », « the clever girl », « the pretty chick » etc, which ultimately came pretty close in end result to « what they do » archetypes.
Then there are a few classless (or almost classless) rpg like the new Alien RPG series and the WEG Star Wars that use archetypes to give examples of characters, but ultimately these archetypes are just guides to justify specific builds.