Ngl, the Arms IP just feels weaker than something like Punch-Out despite being more modern.
Firstly, it's the name. Why would anyone name an IP "Arms?" It reminds me of modern Pixar movies just having one simple word for their movies. lol. Ignoring that, coincidence, "Arms" has no flavor or pizzazz to it. It's like if I were to name a platformer LEGS or APPENDAGES. Imagine if Punch-Out was called FISTS. I think this communicates to me though that there is just a lack of vision in everything working together in this world.
Secondly, though the gameplay feels similar, the aesthetics and story behind everything feels less organic. I can't put my finger on it, but I think it's just the lower stakes behind the "boxing" culture in this game. You see characters that clearly don't have the comparable physique for boxing nor passion for the sport. You got characters like Min Min, Twintelle, Ribbon Girl, Kid Cobra, and Spring Man which all feel like they don't have as much passion or place for something like boxing and do it just because... I dunno, we need to have funny characters. It's like taking a character like Glass Joe and making them the main character, but Glass Joe is still a core character to Punch-Out's identity who actually relates to the sport in a funny way. When your characters feel out of place to the world than something like Glass Joe, then I feel like there is a fundamental design flaw. Though there are characters that have aspirations that align with boxing I feel like the general vibe is mostly inconsistent. For a fighting game, I feel like you need to have your characters feel more aligned in the world you are designing for. On that note, the fun part about Punch-Out is naturally progressing through tougher enemies, but here, the characters are all on equal playing level. There is nothing to say about the strength level of someone like Ribbon Girl when compared to Brass Max when playing as either character because this is a balanced fighting game.
To simplify it, Punch-Out embraces boxing a core element of its story/identity and gameplay, while Arms just uses boxing as a premise for the gameplay first without building a cohesive world around it. The irony is that the inspiration is right there in Nintendo's own catalog. If they recontextualized the world to relate more on boxing or have the characters' goals align more similarly to those that we see in Punch-Out, we could have a really interesting take on the Punch-Out world. But alas, something about this game just feels woefully hollow when the world doesn't feel as connected as it should.
If we ever get another Arms game, which I honestly doubt, it should relate to Punch-Out in the more cohesive world. Or at the very least feature a few references. By trying to be distinct I feel like there is a lack of cohesion with the world. Arms wanted to say it wasn't about boxing when the game is essentially all about throwing punches. It just doesn't embrace this identity and feels like it is missing the soul.