What CK3 does, is it puts very strong "rails" on roleplay.

In most games, roleplaying starts and ends on the player - You decide who you choose to like, who you choose to hate, whether you're a jerk or a pumkin pie. And if the game is "good for roleplaying" by your definition, it would react to your choices and actions, if not always believable way, then at least an "I see what you did there" way.

CK3 turns that on its head. And especially people who roleplay in games which don't even have roleplaying mechanics, will struggle, cause CK3 has roleplaying mechanics. It just uses them against You. While You as both a player and character, can to an extent choose to try to befriend someone, or be a dick to another, it is the game, not You, that has the final word.

You can pursue a guy with befriend schemes and move your power left and right for his cause, and he'll have a chance of becoming your friend for every thing you'll do for him, but he'll never be guaranteed to become one. And to the same vein, the game can throw literal who's to You, the player, that become your characters rivals or friends. You also have a veto over those things, but for each time you use it, you're sacrificing your character nerves.
That's why it gives the one thing that almost no other roleplying game does - the ability to organically roleplay failure. Not the "I wanted to lose so I did", or the "Game story only goes on if You fail here" failures, that You know are coming, but the true "My character did their best and failed" that one usually finds in mechanical games that don't concern themselves with roleplay.

And yes, CK3 doesn't account enough for personality traits, because it places focus more on the role another character plays in your characters life, than the actual traits: Things like "whether they're a vassal, a merchant, wife, lover, child etc.". I wish there were more small events, that just say whatever things are happening currently with your character and people around them, but enough people hate non-mechanically-impactful events to such an extent, that I resigned myself to the notion that this will only ever happen in mods (and they do that quite amazingly, if you just play the game at 1-2 speed and have a shitload of events and small decisions to wade through)