Fifth Dimensional energy is just a lie, mxyz & forger have an agreement to trick & isolated Superman, because supes with his idealism is threatening forger's plan to replace the whole multiverse.
External power or Temporary power are common in DC, otherwise they cant be written as a hero in the city. Tdk also got power from external, and also anti crisis wonder woman.
Ww need whole living things to get her anti crisis ww. And to have the power she need to put his lasso to the forge world that rich of tenth metal, the substance inside every living things. So when she put lasso to world forge she able to tie everything with her lasso at the same time. This is extreme situation external power but she have it in her profile. At this point she needs whole characters and more + world forge because she cant tie everything with lasso 1 by 1.
We also planning to make king omega Superman profile, supes get that power from another character. And doomsday collected that power by countless planets, realities. Which is also extreme situation external power and that power fades, Superman will lost it at the end of time.
That's just my question