Ah, I see. I'm talking about the mechanical context of the D&D game system. In both real life and on online forums, I've seen newer or more casual players try to bringer fully realized character ideas that were formed with a complete disregard of the mechanics of the game.
Character's power is tied to their level, and most campaigns start at a low one. Spells are a limited resource and do specific things with a fixed power level; the Shape Water cantrip does not make you a waterbender. PCs are designed to be part of an ensemble party, not omni-competent lead protagonists. You will be advancing along the path of a fixed class progression, and while multiclassing and homebrew are a thing they have limits.
Too often, I've seen people advance detailed character concepts that ignore all of those, and get defensive when told they have to make a D&D character inspired by their favorite film or comic character and not a direct copy.