There is literally only one hard-and-fast rule in D&D character creation, which is one of basic courtesy to the DM and others–you have to create a character who, for literally any reason at all, would join an adventuring party.
(Like I said, this is basic courtesy; nothing is worse than the player who, when the DM introduces a plot hook, responds with “but why would MY character care? why would I get involved in this monster attack? MY character would just let the town guard handle it!”
The answer to “but why would my character want to get involved?” is “Because you’re not the only player at the table, and you’re not the main character in a novel.” Pulling the session to a grinding halt around your character’s…lack of interest in the entire game….is rude and unfair. This is a team-based game, and an understood rule of conduct is that you are going to be playing a character who will–reluctantly perhaps, warily certainly, out of fear or self-interest by all means, but will nevertheless–join forces with the rest of the group and have some form of engagement with the plot)
And get this.
The vast majority of players snottily talking down to the actually interesting and engaging character concepts for not being “realistic” enough? They violate that one rule all the fucking time. A lone-wolf jaded rogue sitting by themself in the corner might be “realistic,” but if they keep no-selling plot hooks and refusing to engage with the plot because “it would be out of character”, then they’re not a good character for D&D and their players should have made a better one.
Literally the only law of character creation is to make a character who will in some way, shape, or form engage with the fucking story.
Make characters who are INTERESTING and ENGAGING and FUN TO PLAY and yes, don’t let assholes ruin your fun, but also: You are probably objectively better at this than they are and you deserve to keep that in mind.
NEVER take character criticism from people who only have one rule they’re expected to follow and still can’t figure it out.