It’s better than the base game.
The Isle of Armor is pretty fun. It’s not too meaty but having a new wild area is great. The story isn’t anything special but the characters are really funny (particularly Klara, I feel bad for Shield users who don’t get to experience her. The best line of dialogue in the game comes from her.). There’s honestly not much to say, it’s just very fun.
The Crown Tundra on the other hand, is actually pretty great. The whole tundra is open to explore, and while there’s a bit of story you have to take care of, for the most part your left to explore and discover the legendaries at your own leisure. Once again the characters are very charming, the exploration is engaging, the snow capped forests are probably the best Sword and Shield has ever looked. And it gives me hope that the next generation will be fully open world.
If you enjoyed the base game, you’ll definitely enjoy the dlc.