I still can't really believe that they actually managed to make me care about the box legendary.
Let's compare them to the SwSh box legends. We kinda meet them at the beginning, and there's some inherent mystery surrounding them but other than that, they don't really matter during your playthrough until the stupid bullshit with Eternatus which also felt extremely disconnected from everything else. It was so poorly implemented that I didn't give a rat's ass about any of the shit that was going on. And then the dog shows up cause he's a plot device and helps you or something. In the end you don't care about Eternatus or the box legendary, it's just some "epic" shit that happens because the plot decided it had to happen now.
In SV, you are actually intrigued about the box legend. It suddenly falls from the sky, no idea where it's from or what happened to it. And the first thing you do is give it a sandwich. It's a little goofy but it was very unexpected and it made me smile. Then we can see its fully powered form, which looks menacing and impressive. When you get surrounded by the Houndour and it grabs you to save you, it feels like a really cool moment even if nothing really happened. After that we meet Arven, who clearly knows more about Raidon but doesn't want to tell us. That adds more mystery to Raidon and Arven himself and makes you curious, wanting to find out more. So the story successfully hooks you right from the start.
Also even though Miraidon and Koraidon serve the exact same function and have the exact same story, they seem to have very different personalities. This is solely conveyed through their animations, which is very well executed, especially for GF standards. Again, compare that to the animations of the Za's in SwSh. Everyone knows the famous "turning around" animation that everyone made fun of. Presentation matters a lot for something you are supposed to care about. SV did this right.