I feel like some people who don’t get the “everyone is the protagonist” line about Arms don’t really understand that there’s often times a difference between the protagonist of a fighting game series and the face of a fighting game series.
Like, for example, Scorpion is the face of the Mortal Kombat series, but some fans would consider someone like Liu Kang to be the protagonist. Really, it’s usually very complicated who the protagonist of a fighting game really is and a lot of fighting games really don’t have definitive protagonists because of how they’re structured.