RPG elements to me is when your character's ability to succeed at a given task increases without requiring the player to get better at controlling the action that performs this task.

Your character gets better at intimidating others. It's not you as the player who is performing actions in a way that is more intimidating to the target.
Your character gets better at aiming a gun, it's not you who's gotten steadier on your mouse arm.
Your character is swinging the sword harder, it is not you who is pressing the button harder.

RPG elements.

When I say "your character", this doesn't have to be a literal character. Any permanent extention (one that you can't lose) of the object you are controlling counts. If you're in an action RPG where you have guns, can upgrade the stats of these guns, and can't lose the guns, then the upgrading of these guns is also an RPG element.