Personally, I hate that somewhere along the line, we had to make a distinction between "mundane" and "supernatural" to begin with. I remember a time when Dwarves could make magic weapons and armor for no other reason than they were Dwarves, no spellcasting required- the same Dwarves who were so resistant to magic they could only be Clerics, mind you.
Everyone and everything is magical in D&D; the PHB tells us that the stuff of magic is found in everything in existence in Chapter 10, when explaining the Weave. Sure, not everyone can use this magic on demand, but it's there, so any time a character accomplishes something we Terrans would deem "impossible" or "supernatural", that's your explanation.
The need for some to wall off certain characters and say "nope, this guy is 100% normal" in a world where "normal" includes Owlbears, Trolls, and pointy-eared guys who can warp space to teleport short distances 1/short rest baffles me. And no matter how extraordinary the feats these "normal" characters can accomplish, be it the astonishing recuperative abilities of the Fighter's Second Wind, or the time-bending properties of their Action Surge, the ability to somehow resist swords and arrows of the Barbarian's Rage, or even the Rogue's ability to find a vulnerable point to deal additional damage with Sneak Attack against any creature they encounter, whether they've even heard of it or not- some people refuse to entertain the idea that anything unusual is going on, or that the existence of these abilities is evidence or even justification for allowing them to perform other extraordinary feats without explicitly stamping the word "magic" on them.
