Being an unrepentant dog hater myself, I was thinking of bringing up a Pokémon like this myself, but Dachsbun is not the worst one to me.
It's the Maschiff/Mabosstiff family.
Why oh why did anyone at Game Freak see the need to introduce three new two-stage dog families in the same generation? There's Fidough/Dachsbun, Greavard/Houndstone, and Maschiff/Mabosstiff, which all feature roughly the same base design and work roughly the same mechanically. They're single-typed Pokémon that evolve by level at 26/30/30 and have a BST of 477/488/505.
With three sets of dogs in the game, at least they should be distinct somehow. Two of them are. Fidough's bread theme is wonderfully unique, and Greavard takes the "the only good dog is a dead dog" thing to a whole new level. But Maschiff is just ... awfully generic. It's a quite basic mastiff design, its typing is quite bland (pure Dark), and its movepool is nothing to write home about. Sure, it has a unique ability, but it's very situational. Mabosstiff is essentially a physical Houndoom with no flavour. With two other dog families in the game, why add a third one if it's this generic?
My theory is that they needed a dog for the Arven plotline. But Dachsbun wouldn't have the same emotional impact ("Oh no, my pastry dog is hurt!"), and Houndstone is already dead. The writers wanted a Pokémon players could sympathize with, hence they made a dog that looks a lot like a real-life dog for that story, rather than some goofy design.
Also, Gen IX is slightly lacking in Dark-types. Okay, there are ten others beside the Maschiff family, but Maschiff is the only one that can evolve. So it's not entirely without a purpose.
Mabosstiff doesn't feel like it fits amazingly into the narrative role it was given either. As a Dark-type, and not one that has other clear associations besides being a jerk (compare to Darkrai or Absol, for example), it feels completely reliant on being a dog to convey it being a loyal companion. As someone who's most vivid memory involving a dog is being hospitalized when I was 4, this fails on me. Thinking on it, a lot of my own "it's okay buddy, I'll get you through this" moments have involved computers, so Arven having magnemite or something like it would probably produce the desired emotions in me a lot better.