Li Shenron
Legend
Generally speaking, I hate "gamist" mechanics with too weak or no association to the narrative.
In 5e the closest thing to that is possibly the "Lucky" feat. Basically anything that says "you get this bonus or reroll because you're a player character, so you are supposed to win the game" is not to my taste. I can live with one feat like that in the game, especially because at least it has a cost (it costs... one feat!), but I do not want to see stuff like "hero points" or "action points" or any other I-win-buttons in the default game.
I also generally despise "retraining rules". If a player has a problem with a previous character choice and finds out she's never using it, she talks to me and we arrange a retrofit of her character. It's not a problem to discuss something like that between DM and players, but it's awful for the game to grant this right by default to a player. Fortunately, 5e does not exactly have retraining rules... yes there are instances of for example swapping a known spell for another, but this actually always allows to drop a lower-level spell for a higher-level spell, so the purpose is not exactly to change your mind but to actually get a small enhancement as you level up.
The worst thing however is probably "factotum" characters, those which can cover one role on one day and another role on the next day. For me, a character that can do anything anytime, or can do anything on different days, is the bane of roleplay games, because it throws the meaning of "role" away.
In 5e the closest thing to that is possibly the "Lucky" feat. Basically anything that says "you get this bonus or reroll because you're a player character, so you are supposed to win the game" is not to my taste. I can live with one feat like that in the game, especially because at least it has a cost (it costs... one feat!), but I do not want to see stuff like "hero points" or "action points" or any other I-win-buttons in the default game.
I also generally despise "retraining rules". If a player has a problem with a previous character choice and finds out she's never using it, she talks to me and we arrange a retrofit of her character. It's not a problem to discuss something like that between DM and players, but it's awful for the game to grant this right by default to a player. Fortunately, 5e does not exactly have retraining rules... yes there are instances of for example swapping a known spell for another, but this actually always allows to drop a lower-level spell for a higher-level spell, so the purpose is not exactly to change your mind but to actually get a small enhancement as you level up.
The worst thing however is probably "factotum" characters, those which can cover one role on one day and another role on the next day. For me, a character that can do anything anytime, or can do anything on different days, is the bane of roleplay games, because it throws the meaning of "role" away.