[LordDragonfang]

While I agree it's a red flag in many cases (power gaming is an issue), I think you already provided an adequate justification for it yourself: ttrpg play is a community told story. While you may want to play a type of game where the DM is always fully in control, I've played at tables where the DM intentionally gives up some of their control to the more experienced players, sharing the load of creating the world. There are even whole systems where this is an intentionally encouraged mechanic! Even giving overpowered stuff isn't fundamentally different from a DM dropping in an overpowered DMPC to help step in when the players need something.

D&D is intentionally a collaborative story, and it shouldn't be out of the question for players to collaborate with the DM. Focusing on "the balance between player and GM" is great for a dungeon-crawl style game (which I would argue is the only thing 5e is actually designed for, and is poor for what most people try to use it for, but that's a whole other rant), but putting too much focus on it in a more roleplay-centered campaign can lead to a very adversarial relationship between players and the DM. If you have great players, you should trust them to collaborate with you, not just opposed to you.

[joe_the_user]

Oh, giving the player power to make a world and otherwise help in GMing process is fine, something I do sometimes. The thing is, a reasonably skilled player can do that without it involving adding power to their character. Indeed, I've seen this device make players less "power-gamey" because it makes them think of the larger picture, they want to interest the other players in their story etc.

But I don't think this really relates to "my character has excess-or-god-like powers but I won't use them" situation. The point isn't the characters can't have more free-form powers that GM interprets sympathetically. The point is if the player has to say their character has special over-the-top-powers, they are creating a rule, not leaving things for free collaboration. I remember in a FATE game in which one player specified has character's aspect that "world's greatest thief" and this both abuse of the FATE system and actual harassment/psychological abuse of another players. I learned the lesson that aspects never should superlatives to them.