The best way I've heard the D&D level progression put was this way; the power dynamic was designed to change every 5 levels creating games that look something like this:

Levels 1-5: Gritty fantasy
Levels 6-10: Heroic fantasy
Levels 11-15: Wuxia
Levels 16-20: Superheroic

This was said with regards to 3e but, power creep, aside it still seems to be pretty true to 5e.

So even from level 1 you're still head and shoulders above a regular person, this is also expressed when you roll stats, typically you are rolling your stats so that their average is above what the 'average person' gets (i.e. a bonus of -/+ 0)

I think it's Warhammer where you start out with a bunch of level 0 characters and whoever survives the first session is your character at level 1, so just assume your guy is the one who survived to be level 1.