You are incorrect. Silver snow has the worst story of all the routes, it's essentially verdant wind but with a final boss that comes out of nowhere and hilariously fails at trying to make you sad. Some people say Nemesis came out of nowhere, but he really didn't. The opening cutscene of the game was literally him fighting rhea! Were there any discussions in the game about rhea's dragon disease before the battle with her? No, there weren't. However, Nemesis was indeed mentioned before his resurrection in the final chapter. He's an amazing boss to end the game with, and seeing the goofiest house leader defeat the most pure evil asshole with the power of friendship was awesome to see. Does he fit thematically? Maybe not, but he's still amazing and the final boss I definitely loved the most. And if it wasn't for his theme I wouldn't have played the game. So while he doesn't have a trillion layers of symbolism or depth like rhea or edelgard, he simply manages to work for me by being a badass final obstacle to my favorite route.
So basically, silver snow is verdant wind but without the awesome finale. Don't bother with it. Doesn't help that the black eagles are my least favorite house too. It's basically verdant wind but with a trash final boss (that's carried by good music) and a mediocre set of characters.