You're not the same person that you were on the beginning. You have a character growth, story of your role in that world and how you affect it, as character growth this resembles it perfectly you have character that you personalize and upgrade (class/skills/weapons&armor/oufits), consequences are happening of your actions in the world. There is a spectrum of rpg call of duty and mario being the most lightest rpg a slightly more heavier rpg's like fallout is next after that is in the middel of the spectrum all the early console gaming rpgs like pokemon, final fantasy, those story based rpgs and then the heavy side of the rpg spectrum is al theose tabletop rpg games and those like computer games, d&d and stuff. Those classical rpg's. Then the very most heavy side of rpg's are the ones you play in real life, costumes and stuff and like you're the real character of the game in real world a physical rpg i would say. Rpg with combat must have combat based at least partly on attribute-derived statics. Inventory must be in all rpgs nd consist of something else than just puzzle items. Rpg is a role playing game so oyu play and act through a story. Rpg has a basis of game that is building a character of your own. Your stats levels and such affect the story. The game is based on definite rpg system and plays through it. Therefore games like call of duty and fifa and madden and any game with stats and leveling systems are not rpgs because they dont focus on story they focus on f.e. action. The stats and such, through them you play the game, the system of action game is different of a rpg system f.e. action game system doesnt have character creatom freedom, usually you are given character and its in that world, in rpg you act and play in action game you play ts like comparing acting and playing soccer in real life. RPG is like real life but in another world, the aciton game is reali life in another world but restriced to go certain way all the times another player shoots another, story is not existing.In action game you pretty muh know whats ahead, of course there are story mode, but usually in those your role is defined not open and the gameplay is more important, in rpg sotry is more important than the gameplay, in action game the game play is super important. you play rpg to unfold the story and see the characters more in depth to understand hem more and the world they are in plus there is also morales in the story and the world and it can teach you something about the morale of the story. when you think about football games in which players' stat can also grow, it makes you think again. It is not only about Stat, it needs a context. RPG needs a story, in which you grow your statistics. The Management of Growth as the primary method to unfold a Story is what makes a RPG
RPG is kinda like, you know when you see it just like with pornography for example. Every game has same elements of a role playing game, but thats why you can think of it as subgenre, a element, a flavour you can add to your game. the main requirement is it most have character growth (not character development) independent of equipment. I think that is really the core requirement and every RPG follows that definition. Now, to stop other games from using light RPG mechanics, I would say that it must be the core mechanic and thus we can eliminate games like Zelda (as Zelda is and Action Adventure game). Specifically, RPGs are inspired from tabletop games and their main mechanic was the development of a characters growth. That is what I think an RPG should be based on, otherwise Call of Duty becomes and RPG and its definitely not an RPG.