RE: On the topic of Doom/FE in Smash
Having fighters from as many different franchises as possible is beneficial as it enables more aesthetic diversity on the roster. While 'anime' or whatever, Joker brings an entirely new style to the game, as his stage, final smash and results screen are particularly good at showing. And Doomguy would likely do the same: of course we wouldn't be getting the series' characteristic ultraviolence, but the aesthetic and tone isn't like anything else in Smash, making it a nice contrast with Joker/Hero ('anime' looking w/e) and Banjo (western cartoony looking).
Bringing a new series to smash brings much more than a character a music and a stage to the scene; it brings a whole new world that's crossing over. This is good even from a fan perspective, as it brings in loads of fun opportunities for fanart of the various characters interacting. I'm sure a new Pokemon or a new Fire Emblem character would have plenty of fans, but they just wouldn't feel as impactful an inclusion, at least to me (though Pokemon does have the advantage of each character looking and functioning differently apart from the electric rodents- but that's kind of unfair on FE, as that's Pokemon's USP and a reflection of the attention it gets in Smash)
I'm far from being against first party additions to Smash, as there's still several I want, but I'm generally hoping for ones that stand out more visually from the rest of the characters in their series (like a Zelda rep that's not a blonde haired pointy eared person - for the love of god, can we have someone from the series' other races pls)
Though on the topic of Doom, I fully agree that discussing it in Smash has become kind of tiresome, and I welcome this temporary 'what if OverWatch' break, even if I think Doom would ultimately be a good inclusion for Ultimate
Anyways ramble over