Let's put it this way, MJJ was supposed to be an OMNIVERSAL threat. They had to wind up destroying an entire universe just to end the threat of one of his alternate reality selves.
The kicker is, this alternate reality version of MJJ was weaker than the 616 one. Thor, Warrior Madness or Warrior Madness with the Power Gem, would get annihilated. Hell if the hype is to be believed, Warrior Madness Thor with the ENTIRE Infinity Gauntlet wouldn't be enough to take out MJJ.