ARMS didn't flop, though.The main reason ARMS flopped was never due to Spring-Man alone.
It's due to the lack of content , being overpriced for what it is , the game being extremely arcadey (like , fights can last less than a minute) , and the main gameplay while having depth , being pretty simple when you get to it.
And well , that we need some kind of story mode. We still have this visual novel/ARMS comic that is in development hell , but beside that , you have nothing.
They tried to make ARMS the new Splatoon but didn't fully understood why Splatoon worked so well imo.
The franchise deserve another shot , because it has a lot of potential , and while the first game layed the ground works , there is so much to built upon.
It sold 2mil, which while being no splatoon is still pretty darn successful by all accounts for a new IP. What it did was lose relevance rather quickly due to the reasons that you mentioned (no one was talking about it like a month after release). If ARMS 2 releases and ONLY has more characters chances are that it'll fail because it most people don't want more characters,, they want more meaningful content like you stated. It needs more story, more (good) modes, and a better reason to keep playing it (Nintendo really needs to improve their online systems, so they can actually run a ranked mode properly).
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