Right?? I really agree with you. I've seen this coming and I feel like the direction this story takes make it actually interesting? I'll copy paste what I've been wanting to say about this story (I can't post topics atm because mangago isn't letting me :/ but it's been a few days since I've been wanting to write a comment like yours!)
This is apparently a very unpopular take but I really like the direction this story has taken? Cause the concept with diamonds and all was cool, but I like that this hasn't decided to stay purely a "dating show" but to show that there is way more behind it.
I feel like a lot of things were progressively installed only for them to take more importance in the last chapters - like for example we get told about the importance of mermaids somehow through the story of Obsidian for example, only for it to be linked to her acquisition of the egg. And I think there may be honestly more to it, about her, given that so far we don't know the reason why she got it and all.
I also like how Caen's whole existence sets the plot for the politics, the way other kingdoms are under the grasp of the Empire and there is discord but no way to rebel, and that some kingdoms already paid for that (Caen's being a main example). It is even more meaningful when you get to the point that the Jewelry Box is a political device for the Empire to work on their control and influence.
The fact that it's already something that you can think about but that it gets more and more revealed through characters, like Marianne's figure, is really for the best. The crown prince seemed fishy - but the recent chapter only reconfirmed how fishy all the "love stories" are. As for me, I really like that Marianne is not only a pretty doll or oblivious to things but that she carries a real goal and can be cunning and plot along to get to it. Like of course she was a queen so she had to be clever at least a little, but given the presentation we got of her so far - mostly told through the eyes of others, and somehow really under the perspective of the Jewelry box (which I guess is how you know that the Empire worked their game really well), as someone lively glowing pretty that fell in love and that is pretty much a figure of that dating show. Knowing that she's not only that adds so much savor and spice.
Maybe the pacing isn't for the best, but I'm honestly enjoying every new chapter and looking forward to every of them a lot. I want to know what direction this will take, although I mostly think this will be linked to the fall or at least the weakening of the Empire through the different figures that are scheming against it. So... yeah it's just my two cents, but 1 wanted to give a little love to this story because I like it a lot.
So I'm not sure why everyone is hating on the direction of the story, personally for me, the pacing is just like a majority of the pacing in other manga/manhwa/manhua of the same genre, and majority of this information was already pretty easy to see coming and was in fact foreshadowed. The only thing that's throwing me off is the fact that Duke Spes literally looks the same with or without the magic jewel, so I'm not sure how he's hiding his identity at all?