|Bob Bob Bob|
Backstory isn’t what I mean by well rounded. Sure the fighter doesn’t need to be a face but what does your character do during downtime to make them interesting and entertaining to listen to.
Brothels and taverns. I thought that was the adventurer default. No feats, skill points, or class features required. On a different character (not the ablative meat shield who's gonna live life to the fullest before a monster swallows them again) I might splurge a skill point in Craft, Profession, or Perform to indicate a focus on their outside hobbies... but nothing is stopping the Fighter with zero ranks and 8 Charisma from singing every night in the bars, they just suck at it. Again, zero character resources of any kind spent.
What a character does for fun is not a class feature. A character's hobbies do not need skill points. Feats are not required to give a character a family, friends, or rivals. If that's what you mean by well-rounded, any character can be.