The problem is CK3 is a Strategy Game where the point is to control more territory and grow your dynasty.
If it were a Dating Sim what exactly would be the Gameplay? What are you supposed to do?
You Date and do Events to Date and do more Events, isn't that a Visual Novel at that point?
What exactly have you accomplished by shifting things around?
In other words it's the other way around, CK3 is a Dating Sim and VN in disguise.
Well, not exactly. Both Dating Sims and 4X on a base level are resource management strategies.
The main difference is that in CK, or almost any other strategy, land you conquer yields resources that make subsequent conquest easier, and that's an abstraction that's easy to understand because it is very much grounded in reality. In a conventional Dating Sim, a girl does not give you in-game resources that can be used to woo more girls. For one, it's not grounded in reality. Dating someone does not make dating other people easier, quite the opposite. More broadly, pursuing two goals simultaneously is a bad idea, pusruing two conflicting goals makes you a protagonist in a comedy of intrigue where the audience laughs at your self-made misfortune.
And second, on a game-design level land in strategies and girls in d-sims fall into different categories. Land is a square on the game board. A girl is most often just an obstacle course with a prize. It's not ideal, but at least prizes are coveted, whereas land invokes no sentimentality. The analogy of CK would be a dating sim that has adversarial AI that tries to conquer the girls if the player neglects them. I think I can almost hear the NTRRrrrrreeeeeeeeeeeeeeeeeee screech that would follow such a game. Turns out no one wants rivalry, not just fictional love interests
Or I can envision another game where your dates are board squares. It would be called a Golddigger Sim. Date a low lvl simp, wring some money out of him, upgrade your looks and use it to go after a higher level simp, and follow this progression until you harpoon the mega-whale endgame boss. It would work from a game design perspective, but if OPs goal is to have players to form some attachment to the characters, it would fail miserably. The attitude this mechanic fosters is extreme callousness.
I am not trying to distill the concept of a real-life-human-relationship into its essence and inject it into a video game. I am more wondering, what games did it pretty well without being a 50 hour visual novel or Baldur's Gate.
Any example I can give would be a visual novel, or an RPG that achieves what you want with a compelling narrative. It doesn't need to be a 50 hour experience. But it has to have a good writer, and I have the impression that's not the type of answer you seek.
There are two elements I can probably name that are not narrative (but are very much narrative-adjacent). Lively facial expressions and choreography. I peeked at your devlog, and I'm sorry but it seems these are unavailable to you. AI cg, good luck with that, but I prefer crude but expressive art like in
Corrupting a Nun, rather than what AI seems to be able to output. Maybe I'm wrong and you can make 10-20 consistent sprites for one character corresponding to different emotions. If you can, do it. Second, your game seems to be structured like a VN, with no character sprites in a tiled world, so choreography is also flat out.
Better take out your big writer pants from your closet and put them to good use ¯\_ (ツ)_/¯