I tend to agree that this is a wide ranged based on thematic and mechanical aspects to a system, both in initial set and in opportunity.

With very few exceptions (twilight 2000 is the only one I can think of, and even then you’re at least a soldier - maybe DH or WFRP if you go random chargen), almost all RPGs begin with you being “un-average.” Even in the classic D&D sense, a level one player class represents a special skill set and training - you aren’t a turnip farmer or angry peasant. Not everyone walks around going “oh right, yeah, milked the cow today, also practiced summoning demons or calling on a diety to smite my foes and mend flesh. Same old same old.”

Several games go further to make the point - Shadowrun explicitly says that not only do you have whatever skills let you get in to shadow running, the average PC has survived the brutal winnowing process that claims something like 90% of runners in the first year. So in terms of capability, you’re already the hotness.

Others just focus on the narrative starting once you’re competent enough to do more than kill rats. Blade of the Iron Throne just outright says “yes, you start as Conan or Doc Holliday or whoever because that’s the interesting part of the story.”

Even supposed “zero to hero” games like Blades in The Dark mark you as a cut above of the rest relative to your starting circumstances.

From there, it’s a matter of growth thematics. In lower fantasy style games, growth does not mean becoming night unto a god, so you might become a better action hero who none the less never exceeds the capacity that might just be possible from flesh and blood with a light suspension of disbelief. And generally this is easy to make work, world wise. Because fifteen randos are still dangerous to Bruce Willis.

Higher power fantasy like D&D has a much harder problem. Because you do become increasingly god-like, fifteen randos are about six seconds of both, but supposedly the world has enough challengers to keep throwing appropriate challenges at you a the way to being a demigod.