The dwarven battlerager presented earlier by JellyPooga is perfectly legitimate in the default 5e setting, and wouldn't be out of place in many a fantasy setting. It goes against the description of the class as presented in the PHB, but in my opinion, doesn't present an air of presumption that the player can do whatever they want.
The argument is against following arbitrary 'rules' which probably aren't rules to stop awesome and workable character concepts, not that the player can do whatever. Yeah, in a medeival Chinese themed game, don't pull out an expy of King Arthur, dumb***. But what's to say that you can't fluff a druid as a shaman or Taoist caster? But the two are completely different issues.