I mean it really isn't set in stone if they are formed or not, just no one really spoke up about them this entire OOC TBH. Maybe like the Avengers they can be formed later down the road?
From the posts I've read, it sounds like there isn't really anyone standing up for mutants other than Superman, on the 'good' side I mean.
Maybe the Avengers, when formed, could be an X-Men style team, fighting for those people persecuted by society. (Superman as an alien, Mutants, etc), gives them something to actually Avenge after all and gives a genuinely ideological reason to be formed rather than just Superman trying to outdo Luthor.
This is just me spitballing ideas here haha, tell me to go and I'll head back into my lair and brood for a bit.