I actually meant MvC3 and my brain just farted.

Ah, okay, that's fair. I do think it also has meaningful differences from MvC3, but it's a much closer comparison

Why? You share the steering wheel in every moba, you share the steering wheel in every hero shooter.

I explain why, because in those games you are actually independent characters, which is not true in a tag fighter. Short of dying, you basically never need to actually sit out of the game in those games, much less get yanked into or out of being able to play by a teammate (idr which one this game does).

Instead what they've made is a fighting game that will forever be niche, serving only the existing fighting game community and not attracting anyone outside of it because at the end of the day it's just like every other tag fighting game. If those games didn't attract and retain a new audience, 2XKO would not either.

I expect League players have been playing it as well, insofar as anyone has been.

If this were true Smash wouldn't be wildly more popular than every single other fighting game.

Smash, mostly Melee and its derivative mods, are my favorite fighting games and specifically what I had in mind while I was saying it.

That's not because Smash is easier to succeed in at high level play, it's because it actually caters to an audience that aren't hardcore, while retaining the ability for high level play to exist.

But the thing is, modern Smash is an excellent example of a game that takes great pains to be extremely accessible in ways that your proposal fails to be. You do not need to practice and practice to engage with fundamental system mechanics in a pretty consistent manner, you simply do not. That is not true of a game with mandatory 2v2 because in that game, as I think you understand, team combos become a fundamental system mechanic. Another merit of MOBAs and hero shooters, incidentally, is that they let you have a pretty wide range of choices with what mechanics you want to engage with and how, which is part of why beginning semi-competitive players tend to like playing healers and such, because it's much more low-pressure and lets you mostly avoid a subset of what are otherwise critical skills (e.g. aim is typically way less important) while working on other fundamentals (like movement, communication, evasion, cooldown management if that applies, etc.)

Incidentally, other reasons for Smash being successful besides the Intellectual Property elephant in the room is the emphasis on customization (e.g. not forcing you to have more than two players) and on single player content (something that you cannot have in this format unless you propose having an AI play the other character). Making people need to play on a team is opposed to what makes Smash successful, and that's in a situation where being on a team with a stranger is more accessible and pleasant because it isn't a tag fighter.

Edit: While I think RondoRev makes good points, maybe I should say that I'm not saying this out of defensiveness for 2XKO. I think it's a shame it's done so poorly this immediately because I do think it has some real innovations, but overall I hate League and Riot generally and I hate their shitty slop being imported into a genre that is already hopelessly polluted by slop, so I'd just rather it die too soon than live for many years. I have no intrinsic interest in saying the game is good or deserves to do better, I just think that the line of reasoning that you're using with making it harder to interface with the game has been shown at length to be harmful and SF6 (for the several things I hate about it too) is a better example of trying to actually solve difficulties with the genre than what you raise, by centering genuine accessibility and extensive solo content.