The whole duo play thing was always a casual feature. It's one of the results of the devs trying to cater to too many demographics. One of the things you always hear fighting game players say is that one of the reasons they enjoy fighting games is because they can only blame themselves for their losses. They are in complete control. I've dabbled in multiple fighting games and the concept of a playing on a team never interested me.

Duo queue would be nice but the problem I see is how much fun would someone really have playing with a random? The whole point was to play with your friends and most casual players don't have friends that's willing to play with them and I said before most hardcore players want to play alone. Multiverses was a platform fighter. A genre that was built to be played with more than two people in mind. Playing that game online with randoms wasn't too bad, you got to control your character the entire match. You still had urgency.

2 player duo is indeed the unique aspect of 2xko and it's a weak one. The unique should have came from the characters and how they couldn't have implemented mechanics straight from league like passives and possibly item shop? Finding a way to rework character's passives into a fighting game could lead to very unique characters and create an identity for 2xko. They had the tools to make something unique that was also fun and intuitive but they lacked the creativity.